Both entities are regulated by the Federal Housing Finance Agency which calculates and sets the conforming loan limit on an annual basis based on statutory guidance.
[1] The Federal Housing Finance Agency (FHFA) publishes annual conforming loan limit (CLL) that restricts the highest origination amount for a mortgage that can be purchased or securitized by Fannie Mae and Freddie Mac.
By virtue of the laws of supply and demand, then, it is harder for lenders to sell the loans, thus it would cost more to the consumers (typically 1/4 to 1/2 of a percent.)
Congress authorized an increase of the single family residences limits to the lesser of $729,750 or 125% of the median home value within a metropolitan statistical area (MSA).
Statutory provisions also provide for high-cost area loan limits that are defined on a county-by-county basis and can be as much as 150% of the baseline value.