As far as I can tell, you can give this guy as much or as little as you like, and get the binaries. On his ask page, he allows one to donate at certain monthly thresholds, and provides a link to PayPal for one-time contributions. At any amount, you are entitled to the perks or rewards offered on that page. You make a DONATION, and you get a perk. His usage of the word is entirely consistent with the way that the rest of the English speaking world uses the word. You can argue until you are blue in the face that this does not meet the dictionary definition of "donatation," but it is entirely consistent with the way that NPR, public museums, and many other institutions use the word.
I would also note that this is entirely irrelevant to your example of buying a soda at 7-11. Donations are gifts given to charities. One could argue that lunduke.com is not a charitable organization (in which case I would agree that this is not a donation, but that isn't the argument that you have been making), but you would have to stretch the notion to its breaking point to include 7-11 as a charity.