Find your local co-op.
Locally used tires are $5, $10 a set.
Rings are $5 each. So $15
Brake pads, new $25 total
Chain, figure $20
Used triple front derailleur, <$10
That's about $80 for the most part of an overhaul/repair. Add in cables, a new bottom bracket & you're still into it for about $120

New bike? Pretty much. You've gotta do the work though. But it's a lot less work than the time spent at work earning money for a brand new store bought bike.

I suppose it comes down to labor cost & tool cost. If you have access to tools, & someone with know-how, it's a no-brainer. Even so, the devil you know...the bike that you buy for $500 new won't be as good as the bike you built for $250 with higher quality components & the knowledge learned is priceless.

How's that saying? Teach a man to fish...