Allowing your engine to rev more quickly
having 40% less rotational mass on the driveshaft
having a driveshaft balanced for higher speeds
easily worth the $250 bucks, in my opinion
Reducing unsprung weight is one of the most worthwhile mods you can do. (IE: lighter K-member, lighter driveshaft, flywheel, lighter wheels and tires are an easy one too - a stock motor doesn't need 11 inches of tire or wheel on the back)
I spent several hundred dollars on items that don't help with HP or suspension, but was money well spent to make the car safer: window switch for NOS, brake upgrades, HID lamps, Aluminum DS, stupid driveshaft safety loop. Sometimes it worth 100+ dollars to safeguard your current HP levels.