So John, that's why the TR6 I paid $6000 for 15 years ago is now worth
$18,000

One can only have "equity" in  property that is an investment, and
either maintains or appreciates (Real Property) If that property is one
that depreciates, then it is not an investment but an expense,because
the depreciation will eventually equal the equity and there will be no
value at all. Vehicles are machines, they depreciate in value and thus
any "Equity" is eventually lost.

Vehicles are expenses, not investments, depreciate, and thus have a
continualy declining equity, until there is very small residual  value
left. Residual equity if you want to callit thant. Such are the vagaries
of the marketplace.