Why would I pay $35k for a used EV when I can buy a new one for $42k with a $7500 tax credit taken off at purchase?

This article doesn't seem to mention those credits, but they are likely a large factor in the difference between the nominal sale price of a new EV and the used market price.

If you don't factor in those credits, it looks like someone paid $42k for an EV that a couple of years later was only worth $30k. When in reality they paid $35k for that new EV as a net purchase cost.