Ok currently the system is.
$5 = 500 credits
$10 = 1100 credists
$20 = 2300 credits
$100 = 11500 credits
2x$5 donations = 1000 credits,but if you donate in one go you get 100 credtis more
2x$10 donations = 2200 credits,but donate all at once its an extra 100 credits.
In truth if someone has A) the means and B) the willingness to drop a $100 donation into the pot there should be a substantial incentive/thanx given to the donator.In anyone's language $100 is a substantial investment in a Text based game.
Without the donations the game ceases to exist.Without heavy donations the makers dont eat that week (metephoricaly speaking).
For every other increase in payments there is a bonus,except for the real big donation.It should more than anything be these big donations that get the best deal.
I would propose increasing the $100 donation to 12500 credits.
My reasoning. A) substantial enough incentive to make the plunge.B) To show respect and thanx to the players who really want to drop a big hit in.C) The obvious reason that paypal will only take one payment as opposed to five payments,thus enhancing profits and keeping the paying players very happy