Lower volumes across the entire product line will result in higher costs to consumers to recupe R&D costs. GM just sells a ton more motors than any of the marine manufacturers do.
A car motor is not subjected to the extreme conditions an outboard must be designed to endure. Could you imagine starting your car motor, throwing it into gear and running it at redline for 45 minutes… come to an idle and “troll” with it for the next 2 hours and then repeat the max-redline run over and over throughout the day? Boom.
And don’t forget that the marine industry gets the same or more of power per cc / ci that the car industry does but everything weighs so much less and is so compact. I’d venture a guess that a car motor weighs more than a similarly powered big block marine motor… but lets not forget that the outboard also includes “drivetrain” and all electronics, diagnostics and charging equipment under that cowling.
They’re pretty impressive pieces of equipment. Not that I think they’re “worth” $18,000… but if you want a 200+ hp motor, now offered with warranties often extending out past 3 – 5 years, that’s what the going prices is going to be.