Not much of a price difference?!? A summer pass to Tline is in the ballpark of $800, and that is for the ENTIRE summer. So theoretically, if you're really dedicated, you can get in more skiing in the summer than most would in a year, and do it for probably thousands of dollars less than the equivalent time in camp, and not have to deal with that fuckin drive every day to and from timberline.
To OP, you're better off just not dealing with windell's park. It can be difficult to poach... sometimes. I've done it without problem, but not worth paying in addition to the lift tickets by any means, since the public park can be pretty solid.