The cost of the iPhone 8 from eBay and other parts he needed, like the housing and glass panel, came to a total of $390 AUS, which is about $278 USD.
Jeffreys did need to use specific tools from iFixit that cost $60 and weren't factored into the cost of restoring the iPhone. He also used a handy magnetic mat to keep all the screws and parts organized, which cost $20.
Assuming that most of us don't own a specialty toolkit from iFixit or a magnetic mat, the total cost of restoring the iPhone 8 is closer to $358. That's still just under $400 less than a brand new 256GB iPhone 8.
Buying a cheap damaged iPhone from eBay and restoring it seems like a great idea if you want an iPhone for much less than Apple sells it. But taking apart an iPhone and putting it back together is a pretty involved process — and not every damaged phone is damaged in the same way, so it could require more extensive repairs.
The bottom line: If you're planning on trying it out yourself for the first time, expect lots of trial and error, and potentially a totally non-functional iPhone.