For the first decade of Ishar's existance, items had strictly enforced
limits on how many could could exist in the game or in rent.  If the game
wanted one pointy blue hat in the game and someone else had it, it just
wouldn't load any more.  If you wanted it, you would have to convince them
to give it to you, steal or PK them for it, or wait for them to lose it

To keep someone from keeping the only copy of something out of the game on a
character they never played, the game made everyone pay their innkeepers
for each hour they weren't in the game with their limited items, with the
more limited and more powerful items being more expensive to maintain.

This successfully limited the total power of all of equipment in the game,
but strongly favored players who spent every waking moment playing and made
players only able to play weekends unable to maintain a powerful kit.  It
also encouraged PK, hoarding, and made it difficult for less experienced
players to even figure out where items load or have a chance to try them

Since then, we've removed the need to pay rent and the game no longer
considers how many other people are holding an item in rent when loading
another copy.  However, the game still tries to keep everyone from having a
copy of supposedly "unique" items to keep a character's total equipment
power roughly in line with his level.

It does this through a system called "rent points".  Each item, based on how
many are supposed to be in the game and how easy it is to get, has a rent
point value.  And at a given level, you are allowed a certain number of rent

If the gear you are carrying when you try to rent exceeds your total rent
point limit, the innkeepers will refuse to let you keep some of it.  If this
is the case for you, you have three options: level up, dump the gear that's
least important to you, or find a cheaper inn.  Generally, the further an
inn is away from Drake, the cheaper it is.