The problem is the barrier to entry on repairing mopeds is low, and the supply of mopeds is high compared to the demand. Anyone with like 3 tools (ratchet, spark plug wrench, and a screwdriver) can bolt on go fast parts. Rebuilding a motor is worth something more since your average Joe won't be willing to try it. But if there are 10 V1 bikes on Craigslist ranging from $100-400 and one that's fully rebuilt and has new tires/kit/pipe/everything else listed for $1200, then I'm gonna take my $1200 and buy one or two of those V1 bikes and spend the rest on an 80's XT250 or a couple Honda CB125's or something. Once you break $1k you're entering small Japanese motorcycle territory and they are superior in quality, reliability, and speed.
If you can find some dude who had the exact bike you have when he was a kid and hasn't looked at mopeds since, maybe you can get over a grand for it.