Is “It comes with a hitch” an idiom or a simple statement?

Solution 1:

I consider "comes with a hitch" to be something of a set phrase/idiom, mostly because the word hitch (as a noun meaning obstacle) isn't used much in American English outside of a few specific phrases.

The other common phrase that comes to mind is to go off without a hitch, which is used when a plan is executed perfectly, with no problems or complications.

Hitch is maybe a bit more common as a verb, but there it has a different meaning. You may see it in phrases like hitch a ride and hitch up one's pants.

Solution 2:

A more common way to say something similar:

...but there's a catch.

or:

...it comes with a catch.

Catch in this sense means a caveat or restriction. I'd interpret hitch in the sense of without a hitch as meaning almost the same thing: a down side to selling water your rights instead of planting.

Solution 3:

I don't think comes with a hitch is a common idiom at all.

The standard expression is comes with a catch, for which NGrams gives a couple of thousand written instances (but none for hitch).

Ordinarily, a hitch refers to a temporary hold-up interupting the smooth flow of something, as in He spoke without a hitch. You can't substitute catch there, because in the context we're talking about here, a catch means something which [unexpectedly] catches you out. As in Catch-22.