In brief: Intel finally lifted the lid on its Alder Lake processors yesterday ahead of the 12th-gen CPUs' November 4 release date. It will be the first desktop platform to support DDR5, and the memory kits are already available to pre-order---some have been a for a while---but the early adopter tax is evident, and many products are already sold out.
With Alder Lake, which you can read all about here, buyers can choose between using DDR4 and DDR5, though not at the same time, and the type you use will likely depend on what your motherboard supports.
Those opting for DDR5 will get all the memory's benefits, such as access to XMP 3.0, but it comes at a much higher cost than its DDR4 predecessor. Looking at Newegg, the site's cheapest DDR5---16GB of Crucial DDR5 4800---is $115, while the only other 16GB DDR5 is OLOy's Blade kit for $159. Crucial also has the cheapest 32GB kit, which is $211.
Newegg's 32GB DDR5 prices climb all the way to $369 for GeIL's Polaris RGB DDR5 5200, which has been available for a couple of weeks now. For those who want to pack their Alder Lake motherboard with 64GB of DDR5 4800, the only kit on the site right now is from Crucial and costs $400.
It seems that plenty of PC fans have already decided to switch to DDR5. The only kit on Newegg not sold out is Crucial's 16GB product that's set to launch on November 4. Amazon also appears to have sold out of DDR5 kits, as does Corsair's website, where they start at $289 and go up to $359.
In yesterday's performance preview, Intel said that DDR5 should be faster for gaming than DDR4 based on its testing but added that mature DDR4 still performs well. We'll have a clearer picture after doing our own tests on Alder Lake and DDR5 next week.
DDR5 is predicted to hold more market share than DDR4 by 2023. One would expect the former's price to be more comparable to the latter's by this time.