The box is $60 now with the HQ maps. I'm guessing the plastic clan mechs and inflation since the original Catalyst box release factor in there as well.
As Lorcan mentioned, the molds for the plastics were based on the older metal starter sets (which are still available on IWM). Each of them comes with 4 of the box set mechs and is priced at $41.95 (except the recon set at $37.95). Going this way would run you about $250 plus shipping.
For reference, you can search on IWM for the lance packs
Assault Lance (Atlas, Cyclops, Hunchback, Vindicator)
Command Lance (Awesome, Dragon, Enforcer, Panther)
Fire Lance (Banshee, Catapult, Dervish, Trebuchet)
Recon Lance (Clint, Assassin, Cicada, Spider)
Striker Lance (Grasshopper, Hermes II, Jenner, Commando)
Support Lance (Zeus, Jagermech, Quickdraw, Whitworth)