I'll preface this with the caution that my math might not be 100% correct, so don't go blaming me if I'm off by 500 snapshots or something. For each item, I'll write how much of each item you'll get, how many times you buy it, and how many total snapshots it costs. Cavs will get a maximum of 15,000 snapshots, so that's the number that I'm using to determine how much most will have to spend.
Make a copy of spreadsheetThere is a link to make a copy of the document in case you want to make a personalized one depending on the rewards you want, along with a screenshot of the spreadsheet.