How about Nature Diet, that is a wet food and certainly helped (and is still helping) Minstrel who had colitis as a puppy. It works out roughly 1.50 a day at the mo as he is still on puppy rations, but this will go down as his feed needs decrease.
Not sure how close the two illnesses are Colitis/IBD - but it may help. Also Wainwrights grain free is another. I think Archie Bean feeds this to her Archie
Minstrel hardly drinks from his bowl at all - as the food contains all the moisture he seems to need. It would probably be the same on Wainwrights or any good quality wet food