I had a buddy that bought one used and got a great deal. It cost him about $300 to switch it over to 12v from 24v. He still saved about $600 overall. I would imagine that would be alot cheaper than doing a 24v conversion on the jeep
if you had the space for 2 more batteries, 24v could have it's advantages.
And you'd be looking at let's say 200$ for 2 batteries, 50$ for some way to mount them safely/securely.
Then figure 75-125$ for stepup type charger for the batteries.
And you'd have the advantage, higher voltage would let your winch wires stay cooler when running.
but, you'd have a more complex system, so take your pick.