Ideas:

5 dollars - a decorative piece of art
10 dollars - 20x super pups (can be sold, so people with lots of money will pay real money to buy these and sell them for lots of credit! Harness the power of the free market)
20 dollars - 20x super stims (can be sold, so people with lots of money will pay real money to buy these and sell them for lots of credit! Harness the power of the free market)
30 dollars - a cool piece of artwork (can shift every quarter to keep interest up) - cannot be traded
40 dollars - a cool rug (can shift every quarter to keep interest up) - cannot be traded
50 dollars - a city enhancement that lasts 1 month, it increases a cities bonus (Improved Job Market, Research Facility, Stronghold...)
100 dollars - a unique crystal for jedi (can be sold, so people with lots of money will pay real money to buy these and sell them for lots of credit! Harness the power of the free market)
1000 dollars - you get god mode for a week