Actually a good price for it would be 699 as firstly it is difficult to make it, secondly people will be amaze by it because not too much game has this feature
500 because it can be abused and etc
make it more expensive its a good idea and brained peoples can do a lot of thing with that
or make same gamepass that will just restrict more than 100-200 part and make it 300 so they peoples will want to buy 500 robuxed one