Coincidentally I heard of a Vegas casino doing the same thing because they wanted to take out their Caribbean Stud game. Here is a general formula for calculating the expected return when a straight flush pays the full jackpot.(((5108*FL+3744*FH+624*FK+40*J)/2598960)-M*0.052243-1)/(M+1)where
FL = Flush win
FH = Full house win
FK = Four of a kind wi
n J = Jackpot amount
M = Minimum ante bet
In your case we have (((5108*150+3744*300+624*1500+40*155000)/2598960)-5*0.052243-1)/(5+1) = 36.858%. So the player advantage is 36.858% of the combined ante plus $1 side bet, or an expected profit of $2.21 per hand.