Niefel Jarl is worth 500 gold =)
TC Consort for 15 gold? When I play TC I pump out consorts like crazy. They're already one of the best units in the game... IMO.
Eunuch for 10 gold? ...to good for a leader, even a terrible one. 15 or 20 gold seems like a good absolute minimum.
45 for a black harpy is too much unless you give them leadership.
30 gold for a forester? I'm not really sure if anyone uses them now...
And considering all of Man's (Avalon) mages are capitol only, increasing the price is painful.
70g Lord Wardens are pretty crazy, too... IMO.
C'tis: Even at 35 nobody will buy a taskmaster.
Bane spider at 70? ... No, I refuse to play against Machaka with that setting
Those are incredibly good assassins that come with 10 death gems worth of magical weaponry.
Empoisoner also shouldn't drop in price considering their potency.
Well, those are just a few preliminary thoughts. I'm think that complexifying your formula to a form like (x^2+.5xy+(a+bc)^1.5)*10+(a^1.2+f+2x)*5+15 might be necessary to get a good result, rather than using a purly additive formula like x+2y+a+5b+c+15. I can't imagine making a purely additive formula that "considered" all of Dominions' complexities.