A question just popped up in my head:
If someone donated more than 100 Euros to GDC and now got his refund (-13.2%), how do you track who donated how much and therefore how much discount he gets on the final device due to already spent R&D contributions?

Example (disregarding the bonus):
If person A donated exactly 100 Euros in the first place then his R&D contribution would be 13.20 Euros. So if the final device would cost 700 Euros he'd still have to pay 686.80 Euros.
If person B donated 200 Euros his R&D contribution would be 26.40 Euros, and therefore he'd still have to pay 673,60 Euros.

Do you have an agreement with GDC to transfer this kind of info? And if you have, how do you manage the organisational overhead this certainly brings?

Personally I'd be fine to consider this difference a true donation, but others might not be.