General, I like the "trade" interface for in game betting as I find it easier to comprehend. As I'm sure you know the price varies from 0 to 100 with 1 contract being $10 at 100. There is an 8c per contract total commission.
I bought at 26, covered most of my stake at 50 and now will leave the rest as its 6-5 bottom of ninth.
BTW the market maker provided 500 contracts ($5000) either way on this game and total trades were 8471.