The savings really comes when you rebuild. I have the Ultegra hub, Rim, $60 and spokes $20. $80 bucks and I get another 21000 miles out of my wheel. I only paid $50 for the 9 speed hub.
I doubt you cheap wheels would give ME 20,000. I'd go through 3 sets by then, not a saving overall.
I had a wheel wear out(brake surface). Had a rim and an Ultegra hub laying around. Spokes from a buddy at the shop and $15 for a new wheel. It pays in the end!
Biggest issue IMO is knowing the quality of the build and doing it myself, it's GREAT! I've paid high dollar to highly rec'd local builders and tandem specialists only to get trash. Substituted cheapazz spokes, bad lacing (blocked valve stmm) and one wheel failing after the first 40 miles. I don;'t get that lowend high priced quality carp when I build them myself!

. That's makes building your own worth that much more!