July 2019, check the Zen2 thread, OCUK launched the 3900X at £479 and were forced to stick to that price due to an agreement with AMD for initial few weeks. It went up after that to well past £500, supply and demand, and then over the following 10 months after than it slowly went down. The MSRP was £479, and AMD have officially reduced that now, to £419 (maybe £429), and they replaced the £479 price point with the XT. The MSRP is £479, just UK shops are screwing people over as usual, if you buy it from somewhere in the EU and pay in € it will cost you £470 shipped, so the same price as the 3900X was.
Is it worth the difference, no, are they taking the 3900X out of the market, probably not. As i have already said this allows AMD to justify a 'lower' tier of the same part for marketing purposes and sell a 12c/24t CPU at a similar price to that of a 8c/16t part from the competition, thus giving people a very hard choice to make unless they are a super nerd 240Hz twitch gaming person, and that is all they use the PC for. It's all about maintaining or increasing margins to allow the company to grow.