A friend of mine keeps texting me, touting a bet that he is convinced is great - Each team to score a TD and FG in both halves (it happened to hit in both games yesterday). Parlaying 2 games was a 50 to 1 payout. I had to go through the NFL games this season to count how many times this happened. I got through about 15 weeks and it happened 12 times (in about 225 games). If this is accurate over the long run, the payout should probably 350 to 1. Advantage sportsbook.
My feeling is that the sportsbook will almost always be getting the best of it for these type of bets (long shots with seemingly big payouts). Kind of like betting snake eyes at the Craps table. Stay away.