Originally Posted by cpach

The real world differences in speed in dropping even a relatively large amount of weight (say, 400g)from your wheels isn't great, although it does change how responsive the bike feels to a certain degree. Slightly more aerodynamic rims (including some aluminum options) will probably have a greater impact on speed. If you're interested in running tubeless I do think it makes a meaningful difference, so there's that potential to upgrading. If your stock wheels are breaking spokes that's another obvious reason to upgrade (also possibly get less racey wheels).

This all said by an overweight guy who's riding ~1250 g aluminum rim brake wheels for shoots and giggles, but I'm a pro mechanic buying at cost and consider myself a very good wheelbuilder. Truthfully I don't think it makes my bike magically very much better. The high end tubeless tires on my bike do make it noticeably better.

Most brands have some decent disc road wheelsets under $700. Could get Rolf Echelons for a crazy looking/aero option. I've always been impressed with the spoke tension consistency of Shimano factory wheels--RS770 can be had around $700 for a aluminum/carbon rim. If you want to custom build something nice like DT R460s to Bitex/Novatec hubs (or even brand name stuff, like DT350s) with DB spokes for well under $700 even with labor, and could easily be specced under 1500g.