The local muffler shop sells highflow, and normal cats for 69.99-89.99$. I don't need a shop, I have my own welder and I do my own work. So even if it did have 4 cats, and I wanted the best of the best;

89.99 X 4 = 359.96.

I have my own equipment, so even with tax the most I could possibly spend is 400 dollars.. Your numbers are from WAY to high priced materials, and labor costs. Hell I can find cats at freakin' autozone for cheaper than that lmao.