Amazon currently has a few Estes kits at 40% or more off the MSRP. Visit the Rocketry Deals Finder for links to the kits.
Bellevue Hobby Center is currently offering the Estes Interceptor E kit for under $20. They have a couple of other discontinued Estes kits at bargain prices, too. I have no relationship with Bellevue and do not know how many of the kits they have available. (Edit: The Interceptor E kits are now out-of-stock at Bellevue.)