I ran SUA with lift springs for years in my FJ40 (not really a Jeep, I know). It worked well and had few issues. Last winter I did a spring over, and overall, it's a better rig set up like this, but the $500 mentioned is just the start.
You may physically get the springs over the axles for $500, but you won't get a truck that works well, or performs offroad for that. For instance, I have $500 in the anti-wrap bar alone. You will need to figure in new shocks($350-500), longer drive shaft slip joints($500 minimum), new high steer($500+), and different steering links($300). On top of that, you need to figure the fabrication costs if you can't do it yourself. Done right, assuming you pay someone to do the work, I would estimate $3500 or so. The Jeep world seems to cost a bit less, but you get the idea.
If you are new at the offroad game, stay with the SUA leaf springs. Once you know what you like and where you want to go, then consider the spring over, but only with a thorough understanding of what's involved. If you really want to go 4 wheeling in the big rocks, the SOA is a great set up, but for anything else, I think you will be happier with just some lift springs.
1997 FZJ80 Desert traveller
1989 FJ62-OME, 33s, OME suspension, H55f
1984 FJ60-SOA, H41, toybox, locked, 37s, Rubicon edition
1971 FJ40-SOA, FJ60 axles, 85 2F, it abides