Speaking for myself personally, while there's a part of me who would love to have a photo printer "just to have", I don't want to have to find space for it or worry about running it often enough to keep the ink and heads from going dry.
My most commonly printed size is 12x18 and my favorite paper to use is Hahnemühle Photo Rag Metallic. I can get that printed for $22 with free FedEx shipping.
If I was going to buy a printer I'd get the Canon Pro-1000 ($999) so I could print things larger as I need them. Unfortunately it doesn't take roll paper so I'd have to get 11x17 (Photo Rag Metallic, 25 sheets), which is $120 at B&H. So my initial price would be $45 per print. Obviously the more you print the less the cost will be, spiking again when you have to replace the ink ($699 for the Pro-1000). I'd have to seriously ramp up the amount of prints that I was making (and ideally selling) to make it worth it.
Using the lab gives me an easier way to experiment with different paper types and, recently, I've been having prints done on coated aluminum which is just beyond amazing looking. I've gotten a few 24x36 metal prints done for $300 each which is expensive but beyond awesome to look at. (Not that owning a printer would stop me from getting these, but I'm be less inclined to want to print on paper vs these kinds of prints now.)