The 2k limit is there to prevent significant prefarming for a future use, such as a relic. If the cap was to be raided, the costs of the future uses would have to be raised as well to prevent that step from being "too easy" for those who have their tomes at the new cap, while it would disproportionately affect those who are using them.

These kind of decisions are not done lightly and are never as easy as they seem.

I would rather see the costs of old gear reduced to the point you can buy a full set with 2k.