That depends on the quality of birds you get and probably varies a bit if we are talking local demand. Black tails and especially black tailed whites are difficult to get a good color on. If you do they seem to sell very well but if you don't you might as well have mutts. Solid blacks or solid whites would be easy since even from bad stock you get the same color all the time. You only have to worry about type but they are less likely to be in demand. I've probably had the most people interested in good quality short legged black tailed whites but getting them will cost you a bit. I only have 1 hen left because it wasn't worth it. I have a few black tailed buffs but I plan to turn my flock to mottleds of higher quality (at least short legged) than the others I got and leave the buffs and whites in with some serama roos and bantam EE to sell as small mixed bantams that might lay colored eggs.
Odds are you won't make money no matter what you breed so really it's pretty unimportant. In some areas of the country there is hardly any demand for any japanese bantams. Purebred japs here are actually lower demand than mixed breed colored layers or mixed breed good bantam broodies. All my eggs sold online easily but I can't hardly give extra jap or serama birds away locally.