Bullfrog doesn't really set MSRP as of yet.
But I can tell you, for a NeckBlaster, $300 would almost certainly never happen unless the dealer was going out of business (or making a sale with a tub.)
New, that Jet Pak would easily go for $500-$600 depending on the dealer. $400 would probably be a good place to target, knowing you may get less since it would have no warranty.