It's not to hard to figure out; just stop looking at just the dollar figure and think about what the differences are: fore-end rail, 3-way adjustable buttplate assembly, thumbwheel adjustable cheekpiece w/ QD shelf, drilled and tapped for a rear sight base, and the muzzle turned to 0.750" diameter to facilitate mounting a barrel band front sight for long range shooting.
Do you think the additional hardware is free?
Do you think the fitting and installation costs nothing?
If you were buying the hardware from a reputable place like McGee Stocks, a three-way adjustable buttplate is $110 ($165 installed in a stock ordered from them). A thumbwheel adjuster with quick-detach cheekpiece is $100 for the hardware, $170 installed. The fore-end rails is $20, $30 installed. Then you have the additional machining for turning the front sight tenon on the muzzle end of the barrel, and the extra drilling-n-tapping for the rear sight base - say $30-50 for each of those from a local gunsmith. If you priced the hardware from say, Warner Tool, odds are it would cost even more.
In all fairness, I will say (having used custom adjustable hardware on several stocks for XTC and Prone) that the Savage cheekpiece adjuster is not on the same level as McGee, Master Class or Warner. But short of building your own, those are your available options.
YMMV,
Monte