Actually that's a Pro Mazda and they run over $100,000. They do have a carbon tub though.
You could probably find a Formula Mazda like this for under $40K used:
Or an SCCA Formula Enterprises, which runs a 4-cylinder Mazda engine, like this for around $35K used:
My boss runs a Formula Enterprises car so I'm pretty familar with it and the other two if you have any questions.