This year Cochrane updated the report on using monetary incentives for smoking cessation. Its conclusions were certainly not what I anticipated
The review located 16 new studies (now 33 trials) all of which had long term (6 month or more) followup. The overall RR was 1.5 and for the 10 studies in pregnant women it was 2.4. And here is the kicker- these are quit rates after the incentives have stopped- i.e., the therapeutic efficacy remained significant. In addition, efficacy appeared to occur even with incentives of $100USD or less (i.e. about the cost of two boxes of NRT). Unfortunately, there were not enough studies of the efficacy if one were to add incentives on top of pharmacotherapy or significant counseling.