Well, now that you brought up this economical update, I would like to make a related suggestion.
What about a discount for multiple

?
Every time people boughts 1

you're charged 0.35€ + 3.4%.
So after 7 donations you've been charged 2.45€ + 3.4%.
If you offered 7 for the price of 6 (for example) in one single donation you would be charged 0.35€ + 3.4%. That's 2.10€ less, enough to cover the price of the

you give away.
Also a bigger amount like that ($15 or 11.40€) one would be fine to be asked as a gift -because I suppose many people here does not earn their own money, and asking parents to make them a gift would be great for them.
Well, just a suggestion.