Stencyl not only has in game purchases for their flash export but for iOS as well. The the tutorial on the subject is very nice and I am glad that they have done this. So if you are looking to make flash games and iOS games then head over to stencyl's website and start making your game.
Game salad had their first pro user web seminar and it was awesome. I understand how hard it is to make something like these engines and last year game salad got a lot of flack from the community for not delivering. But it looks like they listened and they have made the outreach to their customers a priority and it shows. So I am going to renew my membership and if you are not a pro user then you should become one if you want to make games for iOS. It is a very well built engine. Later game salad is going to native code which should make the performance 10 times better according to game salad.
Either way I am very happy with both of these two engines implementing in game purchases. Personally, adding in game purchases is essential as adding a boolean function to your game. You have to have it to experiment and use it and the process has to be easy.