In case you haven't realized you can buy comparable 1TB NVMe SSDs in today's market for around $100. I see the budget Intel 660p hit $80 for 1TB on sale, or high-end Phison E12 drives at $115 for 1TB on sale.
FWIW the 660p has significantly lower throughput (though not 6x by any stretch of the imagination), it's listed and benched around 1800 for reads and writes.
The listed performances are those are that of a 970 EVO (and the 970 EVO Plus improved on write speed, to almost par with read speed at 3500 and 3300).
The 1TB EVO Plus is $250 on newegg. Not as replacement for an existing 500GB, just retail price for the drive. The 2TB EVO is listed at $550, the 2TB EVO Plus is listed at $650.
Most current era laptops use NVMe. Bargain basement laptops might still use SATA, but lets not pretend that the MBP, while extremely fast, is at all unique.
Not to mention that it’s basically 4 SSDs on 4 PCIe buses.
Edit: I don’t really understand downvotes. SSD on recent Macbook Pros does connect to the northbridge via 4 PCIe lanes. And this is not what “but look I can the same for £50” SSD does.
So… they charge half the price Apple does, and if you don't want to pay it you don't have to care because it's a standard m.2 so you can swap it with a retail drive (at which point you have both the original and the replacement for 50% more storage at a lower price), which you can't do with a soldered Apple drive.
Looks like the test is done by just copying a large file and measuring the time it took. This, of course, gives some idea of performance, but they are quite many things that can affect the results.
On the original article[1] the table also shows results from a synthetic benchmark. This shows 2.6GB/s for Macbook and 1.2GB/s for Dell XPS. They also mention that it's a bit apple vs oranges, since different tools were used for the benchmark.
Your article is comparing against non workstation class laptops. Other laptops in the same class put two NVME SSDs in a RAID configuration for double the throughout.