This has been discussed in various threads tangentially (the PPL thread is one of the better ones to read manga-style/backwards) but some raws (Drostanolone, Oxandrolone, Mesterolone, Oxymetholone most prominently but not exclusively) were banned from being produced earlier this year and enough sources have independently cited environmental/pollution laws to be the reason that it's most likely true, though it ultimately doesn't matter for our ends.
Masteron has been back in production for a while and is currently on the 3rd batch at most factories I believe, possibly the 4th at some but labs are still so hungry that these are being preordered and thus sell out quickly until supply catches up with demand. Oxymetholone and Oxandrolone are constantly rumoured to be 'available soon'. The latest news is Oxymetholone being back early next month, with even sources that are usually careful about overpromising finally accepting preorders, which isn't the case for Oxandrolone so far.
Mesterolone (Proviron) is the one you hear no positive news about at all from China; I wholeheartedly suggest following my favourite zombie idol Ollie on his adventure:
Code:
https://thinksteroids.com/community/threads/purplepandalabs-raw-source.134383828/page-2079#post-2815169
None of these raws are going to be unavailable forever but as the lion's share goes to the biggest cats/pockets first, it may take all year to return back to the prices you're used to as a homebrewer.
Hope this helps and I hope posters more knowledgeable than me like
@Iron_Yuppie can correct any mistakes I've made.