Manitou, sorry I didn't see your post last month...
Mirman has the same IQ test requirements for all applicants, even siblings. But:
1) They expect that IQ is heritable and runs in families.
2) Mirman's IQ requirement of 138 isn't THAT sky high.
3) Mirman accepts SB-LM which can skew higher.
4) Approved Mirman testers KNOW why parents are requesting (and paying extortionately for) the test... some are "easier" than others... scores of 138 on the dot are not uncommon...
5) Mirman WILL prioritize siblings that meet the IQ requirement.
6) Parents will often retake IQ tests with various testers to get one result that qualifies for Mirman.
7) Mirman has an IQ requirement, BUT it selects on the basis of "fit" not IQ... once the 138 requirement is met, they'd rather go with a family that is already known to them.

As to Financial Aid. Yes. They give a great deal of financial aid, but:
1) They distribute it in such a way that MANY families get small quantities of aid, and it is rare that families get substantial amounts.
2) Their internal FAFSA type forms are part of the application process, and are seen by their director of admissions before her decisions are made.
3) All family/personal assets are considered part of their application process, including things like automobiles, and material possessions... this creeps some applicants out.
4) Complaints have been made about Financial Aid applications prejudicing the selection process.