My son and I restore old BMX bikes. Here’s a 1984 Mongoose Expert we restored:
I got the bike for $25

and we put about $150 in parts into it. The most expensive thing was the damn split MX seat clamp (not pictured - just got it after a LONG search). We’ve done a few more. I’ll try to get some pics posted.
I have a nice Haro we did “incognito style”. Everybody knows that Mongoose is now a shite WalMart brand. They most definitely were not back in the day, but they are now.
This is my “re-badged” Haro: