Here's my attempt at a summary for you of the modern ones, ranging from the most expensive to the cheapest (but still reasonably high end):
FKV-5 Custom 845 - Black Urushi Lacquer, cartridge/converter, No 15 nib (standard nib selections) $400+

FKK-3 Custom 823 - Transparent black/brown/clear plastic, piston filler, No 15 nib (standard nib selections) $200+

FKK-3000 Custom 743 - Black/Dark red plastic, cartridge/converter, No 15 nib (funky nib selection) prices vary by nib from what I've seen

FKK-2000 Custom 742 - Black/Dark red plastic, cartridge/converter, No 10 nib (funky nib selection) prices vary by nib from what I've seen

FKK-1000 Custom 74 - Black plastic/Dark red/blue/green, cartridge/converter, No 5 nib (large nib selections) $75+

FKK-1 Custom 74 - Clear plastic, cartridge/converter, No 5 nib (standard nib selections) $75+

Standard nib selections - EF/F/M/B
Large nib selections - EF/F/SF/FM/SFM/M/SM/B/BB
Funky nib selections - includes the the above as well as the flex, posting, music and stub nibs
Note: the soft nibs and flex nibs are not available on the coloured versions, only the black one. Also the prices are what I've bought them for or seen them bought for. None of these pens are available through Pilot USA and have to be bought grey market, usually from Japan.
There is a Custom 98 but it has a No 3 nib and is
cheapish.