Mike,
I'm amazed at how much under Beckett some of the cards go for. Not many go over high Beckett so it most be your perceived value of the cards that needs adjusting.
You'll see that July to October is the height of collecting. The rest of the year on Ebay without going in the description you'll get less then 200 cards listed and that is because it will bring the least amount of $$. In my area the last card show is in September until June of next year. I'm certainly not as active doing the fall as fantasy football leagues take too much of my time. Plus Oct - Nov are the best months with the weather, colors and smells in this area not to be outside as much as possible.