I like the idea of adding a die for a useful item instead of a fixed bonus. This way you don't have to calculate the exact result and might obtain another Tengwar. I also understand that a useful item that belongs to me only and that I love using is inspiring. Other than any other item for the same purpose. I also cannot give my useful item to someone else in the company transferring the advantage. Coming back to the example above, using the hammer I'm used to for smithing is something different than using a hammer from someone else. Does that make sense?In the Laketown supplement in 1ed you could buy items on the market as an undertaking, and those quality items added a bonus of +1 (not 1d) to relevant skill checks. This bonus could be raised to +2 at most. That kind of bonus is to me a more fitting bonus for a useful, but not magical, item that does not affect game balance as much. The designers seem to have got rid of number bonuses this time (every bonus or penalty is counted in 1d, 2d etc).
Still I hassle with linking it to the standard of living. Some cultures are then having an advantage over others, as also mentioned above. Do all useful items have to be expansive? I don't think so. A useful item could even be self-made, costing almost nothing. That would even strengthen the bond between the character and the item.
In my future game I currently tend to allow all cultures one (or two) useful items independently of their standard of living. They only should come up with an interesting story, how they got / made the item.