Current gen hardware is about 10-15k. If you buy used or legacy hardware (like what c5 runs on) you can get much more bang for buck.

Here's an eBay listing for 2 machines with similar CPU config for 400+shipping: https://www.ebay.com/itm/INTEL-COMPUTER-48-CORE-DUAL-XEON-24...

Buyer be wear but there are deals to be had. That said purchasing the hardware is step one. Setting up PXE, network storage, cluster mgmt, recycling and upgrade, etc is a full time job passed a specific scale.