One of my biggest regrets was passing up an offer to buy over 200 HP48 calculators back in the early 2000s. There was an independent book store across the street from a local tech school that had bought used 48s from students. There was one professor who required them for her class but she left and they could not move their inventory. They did have some black screen 48GX so I got those, but I should have picked up the whole lot.