My plumber (whose work I like and trust) employs a guy who plumbs but also does minor remodel/construction jobs. He gave me a quote for building a mud-floor, tiled shower stall (36 inches square) for $3600. This includes builder-grade generic tile (or, if we choose and provide our own tile, they knock off $300). Does this sound reasonable? For Big, Exciting City, it sounds reasonable to me, and I am tempted to forgo getting other bids. (I know, I know...) This includes jackhammering up the basement floor and installing a drain. What say you, handy forumites? Thanks.
For having to bust through concrete and do all the plumbing and tiling, I think that's a very reasonable price. You might want to get other bids just to compare the itemization, though. There may be "hidden" costs that this remodeler didn't include for some reason.
FWIW, I ran some numbers on what it would take me to do a similar remodel on an upstairs bath - no concrete demolition, but I will be tiling the floor. I'm looking at around $900 in materials (tile + fixtures), and probably another $500 in plumber costs, and doing the tile work myself. So, your guy must be giving you a pretty reasonable rate on the labor.
Also FWIW, you'll probably find it worthwhile to pick out your own tile. Just ask the remodeler how much tile you'll need (remember that he'll need extra to cut partial tiles).