If you are skilled then you can solo the guy. But I averaged around 500 units worth of items per path. So this includes all the fights, not just the GM. And some lanes it was close to 300, but that would depend on your roster to easily clear the lanes And during the GM fight, most of my revives were team revives. No point in buying single revives since there is no specific counter for GM so you can use all champs, and its cheaper than throwing one revive on a single champ every single time
If you are skilled then you can solo the guy. But I averaged around 500 units worth of items per path. So this includes all the fights, not just the GM. And some lanes it was close to 300, but that would depend on your roster to easily clear the lanes