Re: new cost old motor
The price of a used outboard is based on the price of new equivalent outboards. The original selling price has nothing to do with it. If you need a 25 hp outboard, a new one will cost you $XXXX. That's too much for a lot of people, so they go looking for a used one. The older it is, the smaller a fraction of the price of a new one it will sell for. It's that simple, and is based completely on the supply and demand for such outboards.
Condition, of course, plays a role and, in some cases, collectibility. For example, a 1958 Johnson 35hp Super Seahorse sells for more than a 1959 version, even though they're mechanically identical. The 58 just looks better to most people.
Same thing with automobiles. Supply and demand sets the price, not the original selling price.