PF - How Much CR or RP is Magic Immunity Worth?

[unseenmage]

Especially in regards to Paizo's CR calculator and/or Race Builder.

We use both in our games and allow playing monsters (which in PF treats CR as ECL).

I'm thinking about playing a stripped down Iron Golem as a PC and am not sure which direction to take in designing a lower CR or playable race version of it.

[Rynjin]

Well, Greater Spell Resistance is a steal at 3 RP. So probably 6 RP for Magic Immunity, or thereabouts.

[Jack_Simth]

Hmm...

Lesser Spell Resistance is 2 RP for 6+HD
Greater Spell Resistance is 3 RP for 11+HD

By extension (your mileage may vary), Superior Spell Resistance would be 4 rp (16 + HD), and near-immunity would be 5 rp (21+HD), so real immunity (or near enough) should probably be about 6 rp.

[unseenmage]

Hmm, are you basing that on pure immunity to all spells that allow SR or the oft mentioned Magic Immunity that can be lowered intentionally?

Would there even be an appreciable difference at the abstraction level of CR and race points?