Description lists max points as a constant 250. But it should really be min(250,10 x CL)
250 max would be level 25, does Pathfinder allow level 25?
The wording matches:
Heal , Mass
School conjuration (healing); Level cleric 9
Range close (25 ft. + 5 ft./2 levels)
Targets one or more creatures, no two of which can be more than
30 ft. apart
This spell functions like heal, except as noted above. The
maximum number of hit points restored to each creature is 250.
and then we have:
School conjuration (healing); Level cleric 6, druid 7
Casting Time 1 standard action
Components V, S
Target creature touched
Saving Throw Will negates (harmless); Spell Resistance yes (harmless)
Heal enables you to channel positive energy into a creature to
wipe away injury and afflictions. It immediately ends any and all
of the following adverse conditions affecting the target: ability
damage, blinded, confused, dazed, dazzled, deafened, diseased,
exhausted, fatigued, feebleminded, insanity, nauseated, poisoned,
sickened, and stunned. It also cures 10 hit points of damage per
level of the caster, to a maximum of 150 points at 15th level.
Heal does not remove negative levels or restore permanently
drained ability score points.
If used against an undead creature, heal instead acts like harm.
Anyways, formula added as requested.
Pathfinder has some rough rules for "epic" levels over 20. And an ioun stone can bump someone's level over 20.