Price, for the T50 option 1 set (the set that im running )
you wont have much change from $2000 the option 2 gearset probably a little less the $3000 same for C52 and C56 which are i think the only other geatsets available.
Is it worth it, sure if your running a race engine with a narrow powerband, practical not on a standard road car unless you like using fuel and like cruising on the freeway at 110 in 5th at 4500rpm.
an Albins' gearset will be a cheaper option but take a while.