It depends on the format, the quality you want, and whether you would buy new or second-hand.(posted 9256 days ago)You could pay anything between #20 (UK pounds) for a second-hand 35mm or 6x6 enlarger plus lens (yes, second-hand can be stupidly cheap), to a couple of thousand for a top-notch new enlarger plus lens.
The most important item is the enlarger lens. In some sense, this should match the quality of your camera lens.
There is a sister forum to this one, specifically for printing etc, and you might browse through that one: http://www.greenspun.com/bboard/q-and-a.tcl?topic=B%26W%20Photo%20-% 20Printing%20%26%20Finishing