What are the (new?) FAR Part 141 rules for simulator hours for private pilots?
First, the new rules you're - probably - thinking about are for an instrument rating, not a private pilot certificate. So, that means that your question is essentially this: how much sim time can be credited towards a part 141 private pilot certificate?

Assuming that your son is doing ASEL (airplane single engine land), then the requirements are in 14 CFR 141 Appendix B. You can use a sim for 15% or 20% of "the total flight training hour requirements of the approved course, or of this section [of part 141], whichever is less", depending on the capabilities of the simulator:


  (2) Training in a full flight simulator that meets the requirements of
  §141.41(a) may be credited for a maximum of 20 percent of the total
  flight training hour requirements of the approved course, or of this
  section, whichever is less.
  
  (3) Training in a flight training device that meets the requirements
  of §141.41(a) may be credited for a maximum of 15 percent of the total
  flight training hour requirements of the approved course, or of this
  section, whichever is less.


A part 141 airplane private pilot course must have a minimum of 35 flight hours training (a school can require more hours, but it can't require less than 35), therefore sim time can be credited for either 5.25 hours (15%) or 7 hours (20%). I don't see any way to reconcile those numbers with the ones you gave, although if your son is doing part of a much longer study course that includes instrument, commercial or ATP training then it could theoretically be a result of how his school organizes training time. That seems very unlikely to me, though.

As for your concern about lowering the package price, that's exactly why simulators are used in training (among other reasons) and there's nothing inherently wrong with using sim time instead of flight time for training. Just ask an airline pilot! But it has to be within what the FAA allows, so I can only suggest that you ask his school to put their claim in writing with references to both the FARs and their FAA-approved training program documentation. If they still make the claim, then forward all the docs to the local FSDO and ask for their confirmation.