Luckily my water is doing great thanks so much!

I am interested in a pool heater but have been looking online and they are so expensive! I have researched and the Haywards are closest to my price but still a little to pricey! Does anyone have any advice on where to purchase these for a great price? I live in Iowa so the water is already getting to cold at night. I would love to be able to use the pool all winter but have seen that it's not possible without a really expensive heater; is this true?

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Oh and I guess I should have elaborated a little bit more and explained that I have found some brand new Hayward heaters on Ebay for $669-$739. Is this as cheap as it gets? We just bought this pool and am so not ready to take it down! It was so much work to put up! Leveling the ground and so on........Please help!