I'm definately one of thouse who feels that prices in BattleTech are better ignored, but in the case of this mech, I might point to a difrent reason to ignore the cost:
Does a nation with a tax base of a trillion souls really care about cost when buying ten or twenty high end mechs for prestige mechwarriors?
If it was an Enforcer or Vindicator or Panther, and they plan was to build them en mass, then absolutly we'd be looking at cost and we'd be worried about 10% here and there (though even then we're only looking at a hundred or so a year). But for any Fox customer they're not looking at this the way the Wolves looked at the Timber Wolf (then one would want to talk cost) but as a luxury item. This the mech mech you give out along side giving someone a planet as their personal fiefdom, so thouse who are truely exceptional warriors who have given a lot to their nation (or who are just super duper connected). So even if it were 90 million c-bill equivlant, who'd really care?
That said, of course, C-Bills are broken for a plethora of other reasons, so I don't mostly dwell on it.