TL;DR: One hour 40 minutes per day, six days a week in the arena, translates to
1640 units per week, 85,280 units per year. This counts all the units from arena milestones, and the average units you get from arena crystals. This requires a sufficiently large roster which a lot of players are approaching or already possess. Players will smaller rosters or even less time can still get a big chunk of these rewards because doing less actually generates proportionately better rewards.
There's no penalty for not going all in.
It has been a while since I looked at the arenas, and ever since mastery profiles were added to the game I've switched my arena grinding behavior from chasing 5* and 6* champs in the arenas to grinding for units, looking for the most efficient way to do so (given my own playing time and style) and I thought I would share where I am at the moment, first to show what's possible for a relatively short amount of time, but also because this turns out to be applicable to more than just players like me. As the title suggests, I'm going to describe how I earn about 1640 units per week grinding less than two hours a day for six days a week (no Sunday grind).
The above image is a typical cycle. My absolute best numbers so far are 33 rounds in the featured, 43 in the basic in the trials, but these numbers are more typical (the necessary rounds vary slightly depending on whether I lose a fight here or there, and sometimes I end up just under the final milestone and need to do one more round that is mostly overkill). I get these numbers running 7s only in the Featured, 6s only in the Basic, and ranked up 4s in the Trials. I run recoil masteries for the most part, and I use the Sigil arena express mode, and the combination of the two results in about a 90s arena round on average. So with 116+44+34=194 total rounds, that comes out to about four hours and fifty one minutes of grind time, which we're going to round to five hours. Over three days that is one hour forty minutes per day, less than two hours per day.
For that grind time, I get all the milestones in all three arenas. That's 540 units right off the bat, 270 in the trials, and 135 in each of the other two arenas. But I also get 65750 battlechips from milestones from all three arenas as well, and battlechips convert into units via arena crystals. On top of that, I also get battlechips for each round of arena I do. The net battlechips per arena depends on the rarity of the opponents in the arena which varies. To estimate this, let's assume that my opponents are mostly 7s in the featured, 6s in the basic, and 4s in the trials mirroring the champs I bring in. In that case, we can calculate the BC per match based on the BC per fight victory and the BC bonus for winning the match. Assuming I win all three fights, that would be 540 BC in the featured, 480 BC in the basic, and 375 BC in the trials. Summing all this up we get 149330 BC total including milestones and arena rounds per arena cycle.
The average number of units you get from arena crystals is 1875 per million BC (it doesn't matter which crystal you buy, the average units per million is the same). So we can convert 149330 BC into an average unit haul of 149330/1000000 * 1875 ~= 280 units. This brings the net units per arena cycle to 820 units. If we do this twice a week, we get 1640 units (we also end up with about one million gold using the same tally including arena crystal conversion).
If we estimate a month to be four weeks, that's 6560 units per month. Just as an aside, the total units in monthly EQ between contender, proven, conqueror, and uncollected is 621 units. Which means a player that grinds arena as above and also explores those maps can get 7181 units per month with relatively low effort. Contender, Proven, and Conqueror are all maps you can autofight (with sufficient roster) and Uncollected is either capable of being autofought or trivially beaten with a tiny bit of attention. The actual amount of player time required to explore those maps is relatively low on their own.
If we extrapolate this to an entire year, we get 1640 * 52 + 621 * 12 = 92732 units With a bit more effort, one hundred thousands units per year is achievable without resorting to non-stop grind.
Now, to do this requires a fairly sizeable roster, and even at just an hour and forty minutes per day not everyone has that kind of extra time to grind (there's other things going on in the game, AQ, AW, BG, that take up time as well). So what does this mean for everyone else? What if you only have half the time to grind, or even less? Actually, putting in half the time doesn't return half the results, it actually returns *more* than half the results, because there is a diminishing returns to the grind, even a grind that is taking less than two hours a day.
Consider: it takes me just 78 rounds to get all the milestones in both the featured and the basic arenas, but 116 rounds to get them all in the trials, even though that's the same amount of units: 270. So let's see what happens if I cut the grind down to just those two arenas. In that case, I'm now only spending about two hours *total* per cycle (three days) which is now just 39 minutes per day. That is less than half the original time. In that case, I would be getting 270 units from milestones and 76330 BC, which converts to about 143 units (on average) for a total of 413 units. That is 826 units per week, just about half the 1640 originally calculated for only 40% of the original time.
What's more, if I was spending less time per session grinding, that would mean I would be using fewer champions, and thus using my higher rated champions more often. This means I would be scoring more points per round, and thus gaining milestones faster. In fact, because I tend to grind more rounds in fewer sessions, I'm actually not doing this as efficiently as I could. If I spread my grind out over more time, doing fewer rounds per session, I could probably reduce my overall time spent even more. Even the milestones in the arenas are front-loaded: it is easier to get the earlier ones than the later ones, so someone who was spending even less time than that and not getting all the milestones would be getting an even higher proportionate return on time invested. If 40% of the time generates 50% of the rewards, I would not be surprised if 25% of the time generated 35% of the rewards or more.
Conversely, if you don't have the roster to do this now, then this means the more time you put into it, the more acceleration you will get out of it. Rosters grow over time. I'm at the point where roster growth will only have tiny incremental impacts on my arena performance, but someone with a much smaller roster has a lot of headroom to grow. Every new champ and every new rank up is going to be adding points and speed. This does get better over time.
Lastly, consider the amount of available units compared to things like big sale events. 92732 units is essentially 30k units to spend on three different events, theoretically completely free to play.
PS: if anyone is interested, the amount of gold that gets generated from the arena if you're grinding all the milestones in the matter I describe above is about 112.6 million gold per year. That does *not* count the gold in monthly EQ (that is an additional 60 million gold).
To summarize. less than two hours a day six days a week generates 1640 units per week in the arena, 85280 units in a year. With the units in monthly EQ, that's 92,732 units available to players from game play alone. A completely free to play player would not have the Sigil arena express setting and might take a bit longer, but slightly more than two hours per day without arena express (but with recoil masteries) is probably still reasonable. Doing less than that still generates good results. No arena express and only doing one hour a day would still generate more than half that amount of units.
PPS: this rate of return of units per time spent is almost three times as much
as I calculated for myself back in 2020 under the original arenas. Back then I was calculating about 58 units per hour. These numbers represent
over 164 units per hour.
