My apologies for my confusion... but I thought selling back and trading in were one in the same thing here at WGT. When you sell back your equipment you are given credits (25% of the purchase price) that can be used toward your next purchase of equipment.
Could that not be considered a trade-in discount? Buy a $9.00 driver, use it, sell it back for $2.75 and then take that $2.75 off the cost of the $15.00 driver, making it $12.25.
Ah well, I was never very good with math. =)