It appears what you get for the extra $20 are internal USB 3.0 headers for use with case mounted USB 3.0 ports, an onboard 1394a header, and an extra system fan header. This would be about the right price for those components. It is up to you to decide if you need them.
------------------------------The power supply is the most important component in any computer. Without a good quality one, you usually wind up with a really expensive door stop. Reply to tlmck