Those are boot dryers that you use after skiing to dry boots for the following day. They're always available on eghey at the prices you mention.
Boot heaters fit under the toes and use battery packs to keep toes warm during the day. The complete set-up runs about $150-$175 at most shops, and the replacement batteries are ridiculously priced in the $40-$50 range.
I ended up sacking up and buying my girlfriend some for her birthday. Hottronics @ COski and Golf with a Coupon ended up running me around $150. She loves them though and it keeps her feet from freezing. Which allows her to ski the full day without needing to warm up.