After you find out more info, then you could call a metal supplier
in your immediate area to determine price fairness.
The different alloy and surface design could make a slight difference one way or the other.
Such as mill finish, polished, diamond plate, removed from a ship's deck, yada yada yada,
good luck !!
40 or so years ago, I scored some old 3x6' signs out of a dumpster that were 1/4" thick from
a Navy base I was stationed at in Key West and still have some of it left today.
that stuff lasts forEVER stored vertically outside.
when cutting thick aluminum, I have used a vertical panel saw, 12" dewalt chop saw,
jigsaw with wood blades, and the old skilsaw that throws molten chips like nobody's business.
also, smoothed edges with a regular hand-held router...... use carbide bits when possible.
those pallets should be good for something in a boat !!
Call your metal recycle yard to see what scrap aluminum is going for in your area
then bargain for price with that in mind.
good luck !!