The other case is that you're making a broad search for good deals and don't care about what you buy
Essentially this. Like searching all trade goods for example. I guess a profit filter would work in most cases. But let's say there is only one particular item in the AH and it doesn't meet minimum profit value. You still might be able to resell it above market value since there is no competition.
So I think you should add both features. Or maybe since minimum buyout is arguably less useful you could keep it out of the UI but leave it available as an "expert search term"