I'm not deciding between a M1 Max and a Mac Pro, I'm deciding between a Mac Pro and a PC. I need the high powered GPUs.
Well, if you need the high-powered GPU's, you might wanna wait till the beginning of the next year when GPU's "should" drop down in price. Remember that the price of a PC nowadays is nothing comparing to the price of the high-end GPU. I built a PC with an WS x299 Pro/SE motherboard and Intel Core i9-10920X CPU with 64GB RAM and I paid for it around 1100~1200$. Bear in mind I used my 2 existing RX-580 GPU's.