Hi Larry,
possibly does chew up the card memory, but I've noticed the cards appear to be getting cheaper and cheaper. I picked up a 256mb the other day on ebay for just over $80 USD plus postage. I would have had to pay nearly that much for a 128mb card 2 or 3 months back.

I'll see if I can work out roughly what a backing track chews up.

best wishes
Rikki