I agree that it does seem likely that humans (would) value certain classes of computations.

Someone comes along and suggests turning off this person's emulation on the grounds that no one will know the difference, and we can use the hardware for something else.

You could consider the rest of humainty to be it's own computation, and then it also seems obvious that it would be wrong for this lone emulation to shut down the rest of humanity.

It also seems unlikely that a full emulation of a human is the only thing that's valuable. Perhaps there are simpler patterns we could emulate that would be much better in terms of value per dollar?

The first things that comes to mind are babies and pets. However, I don't think it is as valuable to keep a compuation at baby-level, as it would be to allow it to extend to normal human level (by growing up to an adult, essentially). And for pets, I think at least part of the value comes from the interaction with a human-level computation (since people don't seem to value arbitrary animals used for meat nearly as much as pets are valued). So I don't think that either of these cases could be used as a substitute; at least I wouldn't find it very valuable if we tiled the universe in baby or cat emulations.

It also seems unlikely that a full emulation of a human is the only thing that's valuable.

I actually find this moderately likely, at least in the sense that I think most people would consider it to be very undesireable to not have a "complete" life experience. What constitutes a "complete" life might vary with culture (is death required for a complete life?), but I think there would be some sort of minimum valuable computation.