oh yes. i think i got it. if you put in 1 dollar you can only lose it. you can you more than you put in...
Pr(no corner) = 33/37
Excepted value = -1 X 33/37 = -33/37
Excepted value of one dollar bet = -33/37 +32/37 = -0.02702 = -2.7%
that shows slightly wrong though?