If signup/renew a Powerup Pro membership for year you get a 50% trade-in credit coupon for everything you can trade. It's much better to use the coupon because trade-in values aren't nerfed. The only problem is the coupon is one time use, so do a big trade and that should cover the $15 to renew or signup.
shouldn't it be about time for a +50% TIC promo?
I saw the 50% promo was run March 29 through April 7, 2013 from a search, so it might be awhile till the next one.