I'll repeat a previous statement, once a month/week/fortnight epic roll for 100 gold - that's only a 66% discount, but you may get more people rolling and it's some little trickles of money

It allows people to support the game a little, without breaking the bank - won't make you a millionaire but it would make you some from the minnows

Other ideas, 500gold to turn off the 2 koban auto collect (or just turn that off please? It's a pathetic drain and should be free) 1000g for an extra 10 energy for fights, little boosts like this that are small permanent one time purchases