Given that most people are priced out of vintage Gibsons they want, the 50s-60s Melody Makers, being still made of honduran and brw like their higher priced brethren, are the closest they can get to the golden oldies.
I'm sure Gibson spared what expense they could when they made them - reflected in the thin bodies, hardware, pickups and mounting everything on a scratchplate. I guess some people are also buying them out of nostalgia, the guitar they or someone in their family learnt on etc.
Anyway, if they cost a few bills, slap in some QPs or Rails and you got a nice little rat rod axe, but the market with vintage guitar is what it is.