SRD said:A fireball spell is an explosion of flame that detonates with a low roar and deals 1d6 points of fire damage per caster level (maximum 10d6) to every creature within the area. Unattended objects also take this damage. The explosion creates almost no pressure.
Bold mine. It does not say deals Xd6 damage where X equals caster level or 10 (whichever is less), but has a maximum of 10d6.
SRD said:You harness the power of unlife to grant yourself a limited ability to avoid death. While this spell is in effect, you gain temporary hit points equal to 1d10 +1 per caster level (maximum +10).
From False Life, 1d10 + 1 per caster level with a maximum of +10. However, empowered it gives (1d10+1 per caster level) * 1.5.
SRD said:Mirror image creates 1d4 images plus one image per three caster levels (maximum eight images total).
From Mirror Image, creates 1d4 images + 1 per 3 caster levels with a maximum of eight images.
If you follow the logic of the FAQ for Lesser Vigor, no metamagic feat could overcome the maximums listed within the spells, as they are listed in the same way. "Spell has effect with numeric effects XdX + X per X caster levels (maximum X)."
The FAQ listing is arbitrary. Thus my thoughts is to allow metamagic feats to surpass any listed maximum within the spell as that is the point of metamagic feats (to break some of those restrictions and limitations).