Specifically I am curious how much the phalanx fighter 3 ability (polearm in one hand) or Titan Mauler's Jotun Grip (any 2h wep in one hand) would be priced if given in a magic item, like a glove.
Those abilities replace Uncanny Dodge and Armor training, respectively, in their respective archetypes.
Any precedent items?
In 3.5 the general "guideline" was an item that granted a feat was roughly 10,000 gp. Obviously, some feats are better than others so prices still varied.
Granting class abilities, isn't something that items should do, it invalidates classes as a whole. I don't believe there is a precedent but I don't have my UE book to go through and check (though there may be an artifact that grants spell use as XYZ, but don't quote me on that). The closest you see semi-regularly is items that add levels to class abilities you'd have (Monks Robes, etc.)