They were popular among collectors for their quality and variety. The Nissan Leopard was a luxury car produced by Nissan from 1980 to 1999. The G-10 model likely represents an early version of the Leopard. The high price on the Amazon listing suggests that this particular model and packaging are rare and sought after by collectors. Vintage Diapet cars in their original packaging can be quite valuable, especially if they are in mint condition and represent popular or rare vehicles.
The value is influenced by factors such as condition, rarity, and collector demand.