Hi Mike,
I’ve noticed the same thing with the various types of KD (knock down) wood foundations like this or this that are sold under various names. The quality seems to be spotty sometimes and they almost seem to have two versions based on the feedback I’ve seen. One seems to be up to spec and the other “version” seems to use inferior materials. They are inexpensive though.
There’s also the cheaper wire grid type which are also sold under many names but are all similar like this or this. I’m a little suspicious of using thin wires that have that much space in between them but they are certainly strong and they seem to work well. They’re more of a frame foundation combination though rather than just a foundation.
One of the most reasonable of the higher quality wooden foundations I’ve seen is the Natura universal foundation. Natura dealers may have this for even less.
One of the higher quality wire foundations is the Power Stack like this.
Overall … the best source of a lower cost foundation is usually from the outlet you bought the mattress from. They are usually well experienced in which foundations work well with their mattresses and most of them are very conscious of the need to offer a good foundation with good value.
Local outlets are also good sources as long as the specs are suitable for a latex mattress.
Other foundation options are in the foundation post here … but most of them are more expensive.
If anyone knows of other options for high quality foundations that are good value feel free to post a link here 
Phoenix