What would it cost to make Symbol of Storms permanent?

[Reduxist]

Just because I don’t see it on the Permanency list can’t mean it can’t be made permanent. Judging by the spell level (6), my first estimate would be that it’d cost the same as a Symbol of Persuasion, another 6th level symbol spell. Thoughts?

[OmniMage]

I have made a spread sheet for permanency a while ago.

The pattern for permanency is...
Minimum Caster Level: 8 + spell level
Cost: 2500 gp * spell level

There are few spells that are treated as though they were higher level spells.
Gust of wind - as lvl 3 (+1)
Symbol of fear - as lvl 5 (+1)
Symbol of sleep - as lvl 5 (+3)

0 level spell are counted as level 1 spells.

[Ryze Kuja]

Minimum level: 14th
Cost: 15,000g

But using Permanency is subjective, the GM has the ability to allow or disallow any spell when it comes to Permanency.