islane
(prices estimated from eBay)
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CPU, fans, cpu cooler, motheboard, RAM, PSU, GPU (comparable Radeon 280x) $865 +/-$50 (shipped) Note: a cheaper CPU (+overclock), a different PSU (500-600w would be fine for this system), cheaper ram (+overclock) would net a $100-200 savings for nearly identical performance
Case (Silverstone fortress FT-03) $200 est
Apple-compatible PCIe wifi card $130 shipped
Storage, speakers, mouse/keyboard, and display vary by user needs the cost here could be $200 or less for cheap/used components or $10k for color-accurate panels, audiophile speakers, custom mechanical keyboard, multiple PCIe SSDs, etc, etc
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TL,DR - let's assume you're will to source some used components and go the cheaper route on a few things. You already have access to a screen, input devices, and speakers. In this situation, you could build a comparable machine for under $1000 + the cost of whatever storage SSD/HDD you need. You could stay under $1000 for the whole build if you opt for a cheap case and a single SATA-based SSD.
I would suggest this card, it should work, it is SATA based as opposed to NVMe. I have installed a few of these in on several older systems (x58 based and others) and saw a very large performance bump, even versus SSDs connected via aftermarket PCIE SATA-3 controller (running at 500-550mbs). YMMV if attempting to clone an existing drive - I have had this problem with add-in PCIE cards, older motherboards, and various operating systems - a fresh install to one of these drives will likely be easier.
Granted, updates are generally infrequent, but the consistent (high) quality of the writing for over 10 years is a pretty amazing feat. Much respect for all the DI authors/contributors.
For the uninitiated, the ebay workstations mentioned are typically these ancient x58's. Most support hex core xeons, 24gb ram (or 48gb unofficially, more on server boards and some workstations), and a pile of PCI-express lanes. As such, you can easily add in PCI-express m.2 SSDs, USB 3/3.1, and GPU's to your heart's content. The takeaway is that old pc tech can be had at a fraction the cost of new hardware with comparable performance.
I understand the marketing nonsense from Apple, the "PC does what" consortium, and hardware vendors on the whole - but there is nothing sad about owning an old pc. The reality is that the best performance for the price lies in "obsolete" platforms.