Of course you could donate for 109 farming. i wouldnt reccomend it though. wasting money on a skill wouldnt be a great idea.
however if you wish to go thru with it.
i would say 1 buck?
I would go lower but the paypal fee is 69 cents so i am only getting 31 cents to go for server fees.
And again i wouldnt realy do it man.