So if a uni had to have its hub replaced I am assuming that would require a wheel rebuild. Roughly what would the cost of this work be?
And are there any disadvantages to going this route versus just buying a new wheelset?
The labor would cost probably $30-$50. But you should do it yourself, you’ll probably get a better wheel and it’s a great experience.
You probably shouldn’t re-use the spokes; re-using the spokes will result in a weaker wheel that is more prone to spoke breakage, because of the changes in stresses on the spokes.
Re-using a rim should be fine, unless the rim is bent or dinged or whatever.
usally when i answer you have already made a choice anyway so i might be wasting my time but here goes.
most of the labor is in the wheel build (putting the spokes through the hub and into the rim) get a tutural on net and do that part yourself. Then take the untensioned wheel to a shop and have them true it up…that will save 20 tp 30 bucks at least.
you could do the whole thing, its not rocket sceince but i can understand if you dont want to but at least do the build part.
Well, I’m relieved to say that I haven’t made my mind up on this one yet Jagur! 
I was just trying to figure out if it would be worthwhile to buy a busted uni and they have it fixed up or whether it would cost more money, or in the case of doing part of the re-build myself as you suggested, time, than its worth.
If a unicycle is busted enough so that the hub is dead, then the cranks and rim probably aren’t in good condition and might need replacing, so you’re effectively just going to be buying a frame, a set of pedals and a seat.
Joe