Why do some cars hold their value better than others

[daz75]

I constantly watch eBay and here for prices and was wondering why some cars hold their value better than others.

For example the x-ray cars are expensive from new but seem to go cheaper than associated. Tlr 22 3.0 before the 4.0 cane out was also poor at keeping it's price even with the expensive laydow

The last 2 b64's on eBay have gone got less than £200 despite them only recently coming out which seems strange.