If you look under weapons, the mighty cleaving ability bestows Cleave on the character. That's worth a +2 weapon enhancement, or 8,000 gold. Since weapons tend to double the cost of an ability, i would say that, because cleave is the second feat in a tree, any other given feat would be 1/2 a +1, or 1,000 gold. That's just my logic. Other wise, change the price appropriately.
For example, If you want to give the character a pair of boots that bestow the Dash feat from Complete Warrior, it should cost somewhere around 1,000 gold because it takes up a slot. A ring of greater spell penetration would probably cost about 4,000 gold. That sounds about right to me. Any thoughts?