I don't get car poeple at times ?

Please don't take this the wrong way but?

I don't get why some cars have lots of money in them but not yet finished and told it's not worth the money it has to be sold cheap.
But yet some guy buys a 1000 to 1500$ rust bucket and in the long run spends more time and money just on the rust alone, then it would have took to buy the car almost finished at the price that's been invested in.