HRM - Price Vs Quality

I recently ordered a new helmet from Nashbar and in the box was one of their catalogues with 10% off coupon on it for my first time ordering with them. Was flipping through and saw that they had several HRMs for various prices. Some of them marked down quite a bit, plus I would have another 10% off. I am very very broke right now and so can't afford to spend a ton. But while the opportunity has presented itself to get one very cheaply, I thought I might consider it. I don't really know anything about which brands are better (and I can't remember which brands were in the catalogue), but I guess most people have paid at least $100 (if not more) for theirs? Would it kill me to get one that retails more in the $50-$80 range? Or wouldn't they work as well? I don't need some crazy, tricked out thing. Just to make sure my heart isn't going to explode...