What do you use?
I have no idea, but subbing because I'd love something like this, too!
I don't know of one that does all that.
I used to use Grocery Zen on my iphone ( it doesn't have an ipad specific version) and it does allow you to enter recipe ingredients so you can just tap penne with mushroom sauce for example and it puts all the ingredients in the list. I didn't find it convenient though because most of the time I already had some of the stuff already so I had to delete it.
I've use Shopper, which does have an ipad specific version and it lets you check coupons and I think you can add prices. I never did that though because I don't track prices or coupons. I dropped it because I got sick of the ads in the app.
I now use Grocery IQ it has coupon capability and I'm pretty sure you can enter prices. It does have an ipad specific version, I only use shopping apps on my iphone because I don't carry my ipad with me all the time so I can't really review it as an ipad app.
For recipes I use macgourmet for ipad ( there is a separate iphone app), but it just syncs your recipes from your mac desktop/laptop computer and there is no windows version. It does have meal planning and grocery list making capability but it's not really a shopping app.
We use (and love) OurGroceries. It's nice b/c the kids have it on their ipod touches, I have it on my iphone, and DH has it on his Android. When someone adds or crosses off something, it changes everyone's list. Nice b/c I am often at the store during the day, then DH stops on his way home from work.
I haven't tried any others, though, so I don't have anything to compare it to.
eta: some of the ones mentioned sound really cool. recipes/ingredient lists and even pricing? I might have to look around the app store...