Don't like this suggestion.
But it can be adjusted with some other idea! Gold sink is quite important actually, but people already do not care about upkeep.
Therefore the following stuff could work then:
Looming an item +1 increases the repair costs by 10%.
Looming an item to +2 increases the repair costs by a total of 20%.
Looming an item to +3 increases the repair costs by a total of 30%.
Putting another LP into the item to decrease the upkeep by 10%.
For a +3 item it means with 3 LPs you can decrease the increase of the upkeep from 130% back to 100%.
For a +2 item it means with 2 LPs you can decrease the increase of the upkeep from 120% back to 100%.
For a +1 item it means with 1 LP you can decrease the increase of the upkeep from 110% back to 100%.
For a +1 item it means with 3 LP you can decrease the upkeep to 80%.
LP and Goldsink both. 6 LP per item at its best, 3 LP if you dont care about gold, or 3 LP if you dont care about stats but gold.
Example:
Destrier: Upkeep 1,642 gold.
Champ Destrier: Upkeep 2135 gold.
Long Bow: Upkeep 777 gold.
Masterwork Long Bow: Upkeep 1010 gold.
Danish Greatsword: Upkeep 1,114 gold.
Masterwork Danish Greatsword: Upkeep 1448 gold.
In the end, by having better gear than others, you either pay with gold or LPs.
Obviously no one would care if he got a low upkeep item +3 if the difference is only 1-200 gold. But for Horses it will be a difference, as well as for expensive weapons or arrows.