The two biggest cost considerations, in my experience, is whether you can happily get away with AALs vs. full replacement leaf packs, and whether or not you can happily get away with stock replacement shocks vs. coilovers. How you use it determines which of those two things applies... from there you can start planning your suspension out based on budget.
Biggest mistake people make is misjudging or disregarding their actual intended use by either assuming they need the absolute best, most bombproof system in the world to drive around town and pick the kids up from school every day or the opposite, thinking they can get away with 5100s and an add-a-leaf to do cross-country off-roading with 600 pounds of gear in the back of their truck.