I would like it to be around $20, but knowing OmniGroup and their pricing (OmniGraffle), it is going to be half of the desktop version ($80) so $40.
OF iPhone: $20
OF iPad: $40
OF OSX: $80
If so that will put my total investment in OmniFocus at $140 which might seem like a lot, but not when compared to other POS software I buy and barely use (Office, Adobe Photoshop) isn't so bad.
That being said, OmniFocus 2 is probably 6 months away so I will be upping the anti at that point.
As to where I want to see the price, I think it should be $24.95. That is up from the iPhone (more functionality, etc) but not as high as OmniGraffle.
OmniGroup should just start the price at $0 and raise it $.25 every time someone complains about how long it is taking to release it.