A link if anyone has one will help. I'm clueless on this one.

Good portfolio books seem to run from $50 to $150, give or take.

Or did you mean something else?

If you're asking what photographers pay models for portfolio work, the answer is probably $0. I think... I personally would never pay a model just to update my portfolio. But that's just me.

Edit: Woops. Just read your clarification. Disregard my post.

It depends on the location and the type of "portfolio".  If it's for 'net modeling, you ought to be able to get it for free.  No need to pay a photographer for that.  If for fashion, the fees vary from free to $500 or so, but seem to be centered around $250 for an excellent, agency-approved shooter.  For commercial print the cost is higher; typically from $400 to $600 or more, again for a good agency-approved shooter.

If the photographer isn't approved and routinely used by an agency, or does not routinely shoot paid fashion or commercial jobs with models, again it ought to be free.  The chances of getting something actually useful out of the shoot for a mainstream agency/client to use are pretty slim in that case, so no point in spending money on it.