I didn't realize when we had a new furnace installed that the replacement filters were so expensive. I also didn't realize that they can not be purchased at big box hardware stores. Luckily, they only need replaced every six months. The filter obviously works, due to the fact that it is very dirty when I change it and we seem to have to dust the furniture less often since getting the new furnace/AC. I'm giving a 5 star review because Amazon offers the best prices on these filters.
Note: There are 2 models of replacement filters that fit. The 410 and 413. The 413 filters smaller dust particles than the 410 and is recommended for people who suffer from allergies/asthma. The 410 is typically a few bucks cheaper.