That Celica is valuable because it's a survivor and rare. Just about every other '71 Celica has been crushed into a cube that was dropped into the blast furnace. Except for the rub strips, the previous owner went to some effort to keep it original.

I look up the KBB values of my cars on the anniversaries of their purchase. My 2007 Chevy Cobalt SS has occasionally gone up in value a few hundred dollars from the previous year. It's not because of any collectability, though. There's a shortage of used cars now, especially cheap ones.