Which basically just means 30% off. Still, a number of OSR publishers are participating. In no particular order:
North Wind Adventures, makers of AS&SH. Usually the game itself is cheap, but the adventure are pricey at $10. Now only $7, still too rich for my blood given the previous mixed bag quality, but better. Also not crazy about their shift in art style to comic books. I don't really like comic book art, to be honest. Though it's the older style, not the terrible digital pain style of modern comics which makes them look like South Park.
Three Sages Games made one of my favorite OSR modules, The Beast that Waits. Their other stuff is much smaller, probably because TBTW didn't sell well.
Expeditious Retreat Press, the chaps behind Advanced Adventures which more than anything is what got me into old AD&D. I got their trio of compilations from Lulu. Looks like the 4th one will be a while as they are going out maybe 1-2 a year, but I imagine buying the PDFs would help justify releasing more. (The catch is, the PDFs are hard to read, even with reading glasses, since they are meant for print)
Quasar Knight hasn't produced much OSR stuff, save for a Harry Potter style sourcebook for S&W
Infinibader produced a couple of okay but nicely detailed modules.
Truth & Talismans is a OSR magic sourcebook
Mazes & Perils never really clicked with me, but I was never a huge Holmes fan, since I started with AD&D itself.
Goodman Games. I really did not like the direction Dungeon Crawl Classics went, from the stupid dice to renaming ability scores to spellcasting to the character funnel, But they produced a handful of 1e adventures.
D101 Games produces Crypts & Things which is nice, though I wasn't impressed by the adventures for it.
Judges Guild has its back catalog available, much of which is terrible, but there are some gems, mostly the Jaquays stuff. The Book of Treasure Maps is an underrated gem.