Hi,
the reason for making such a bet is because you believe they will win but not cover the spread.
actually its a very wise choice because the guys making the spreads are seldom wrong.
that said: i’m quite certain the odds makers take this into consideration and if they offer $100 back on a $150 bet ….. in the long run you’re going to come out ahead.
only very, very smart betters come out ahead on any bet. taking into the equation of 10% juice etc …. whatever it is that effects a payout …… the odds makers …. know what they’re doing and in the long run ….. you’ll usually beat the player.
hope that helps.