Jackson guitars makes 99% of guitars with a neck-thru construction and charges more for anything different than that (bolt-on or set-in) even if the neck-thru construction is, usually, the most expensive one; that's 'cause their build flow is optimized for the neck-thru construction and deviating from that makes for more costs for the "special" thing. I think that's the same for Warmoth's compound radius necks, their build flow is layed-out for the compound radius and making a straight one in a "one-off" the main productions. Also it could be, as an "incentive" to the upcharge, that they try to make you tend toward the compound radius to have you buy and use "their kind of thing" instead of "the kind of thing that everyone makes"... hope it makes sense and sorry for any mistake in my grammar or sintax.