I wouldn't spend $400 for this conversion either.

There are modern cranksets that don't look out of place on an old bike and will give you better climbing gears. You could go with a modern square taper compact crank (usu. a 50/34):

Defiant Compact Road Crank ? Interloc Racing Design / IRD

Or you could use a "wide" compact (usu. a 46/30):

IRD Defiant Wide Compact Road Double Crank Set (46-30T)

Grand Cru 50.4 BCD Crankset MK II