Just another thought regarding donations...
Keep in mind that this theme supports both Firefox and Thunderbird. If you use it for only one or the other, use the "specify amount" option to donate a lesser amount (e.g. 50%, or $2.50).
I wanted to point this out as I did not see this mentioned in the posts commenting on the requested donation amount. When you realize this is for two themes in one package, the amount seems pretty fair to me.