I can do this for the princely sum of... 1000 diamonds (or equivalent in rares, my evaluation). Only snag is that I get the creative item.
I believe the current price would be 1500 diamonds, and even then, considering the big amount of money, I'd say it's still a rather bad offer.
From what I understand he is willing to buy someone the upgrade from donor250 to donor400 for 1000 diamonds or the equivalent in rares but you also have to give him your creative item.
Just thought of something after what I just posted, the creative item, I imagine you would choose it and make them pick it for you, but what if its an illegal to trade item and they snitch you out and get you banned after you buy them the upgrade. Haha I doubt someone would but when you have anxiety like me you think of crazy things like that.
It's a good point. In such instances, the creative item would come straight to me and not through the customer.