A sizable number of conventional mortgage borrowers paid high prices for their credit last year, according to a new analysis of Home Mortgage Disclosure Act by the Federal Reserve Board. The analysis looked at data on “rate-spread” loans reported under HMDA, which includes first mortgages with annual percentage rates that exceed the rate on comparable Treasuries by 3 percent or more at the time of origination. For second mortgages, the APR trigger is 5 percent…