Here's an idea: advancing levels with real exp (partial training
included) should halve the cost of those last 10 levels (why not
earlier ones too, but especially 90+).

This wouldn't be an option when reincing of course, and measures would
need to be made to prevent player-mode reincers from abusing this. With
this, advancing the last 10 levels would need "only" 55 2m blocks,
instead of 110. Last levels would still cost 110m, which is still
more than levels 1-90 combined, and after reinc the costs would be
as they are now.

Seriously, exping 2m in one session takes a while. It's not really
hard, and dying is rare in exp parties, but being forced to do that 2m
in one session gets bad. Doing it once or twice, sure. But doing it
110 times (levels 91-100) would just get way too boring for vast
majority of the mud. Seriously. How many have actually leveled more
than 1 level 90+ without reincs. That 2m forces you to do dedicated
several-hour sessions... "I can't come to kill tiamat, I'm doing
levelblock". If you'd only need 4-7 blocks for a level, instead of
8-14, there would at least be some reward for that.

This idea comes from somebody who's well in 100 level, and I'd reinc
the levels even if this system was implemented, so I'd say I'm pretty
unbiased.

-Era of the thrikhren race