I'm in the market for one, so I've researched it a bit. Sorry if it's a bit long. I used startpage and the first result for '20" bandsaw' (that wasn't about MWs wooden one) was this;
https://lagunatools.com/industrial/...btiBIkumQI7eUrnD9Vs1tqLlYMbq99ZltDzAa8eCaNaYN
$6,099. That's 4,787 GBP. Now If you needed to setup a commercial workshop it's probably worth the investment. However most hobbyist (or even small shops) don't have anywhere near 4k. So new market is out of the question. Second hand market or build, are your only options. You may be able to find a cheap Chinese saw, but cheap+Chinese=trash.
Looking for a 20" band saw on the second hand market allows you to find good quality stuff from wadkin, oliver, [your favroite]. BUT unless you get one in reasonably good condition you may end up having to employ a machenist (or learn yourself) to repair it. IMHO a vintage restoration is likely to take longer than building Matthias Wandel's wooden bandsaw. Especially if you buy the plans. Basically SH 500 gets you a saw and 50 gets you a saw that needs a lot of work.
I intentionally have not looked very hard and found this nice Wilson and Startrite saws for 550 and 380. Thats nearly a 10th of new.
Wilson:
https://www.ebay.co.uk/itm/116298806923
Startrite:
https://www.ebay.co.uk/itm/267058227442
Parts can sometimes be nearly as much as the second hand saw. If you need a bigger saw you have to buy (and possibly sell old) another one. Also that Wilson looks heavy, moving it incurs cost, and a hernia. The good thing about a wooden one is that you can replace every part immediately (well except for the time to make it). You can modify it and make it into what you want. MWs workshop was in a basement so access was limited.
I have a pile of wood for free that could probably build most of it. A spare motor is kicking about, I probably have some bearings. If you take the cost of the wood out there's not much to buy.
IMHO two professional joiners with a full set of tools could build this and have it cutting wood in a couple of days. It doesn't look much harder than a router table with a custom router lift. And there are plans. If you're paying them 4k GBP over 2 days, that's 1k per employee per day*. Or spend 4k on the saw.
*Any job vacancies going at that rate?