Beware that that the concept of prime is not necessarily consistent across all banking institutions. Many banks modify their prime rate to adjust their lending strategies, however most out there right now are 2.25%.
You are quoting their "Our Mortgage Prime Rate".Take for instance, the verbiage on the link you provided from investor's group:
"* The Annual Percentage Rate (APR) for each term listed above (with a reduced rate for an introductory period, where applicable) is based on a mortgage of $100,000, with monthly payments and a 25 year amortization. The APR was calculated using Our Mortgage Prime Rate of 2.500% set on March 24, 2009, which is subject to change"