Ebay and Amazon are flooded with it. Especially if you are looking for anything prior to DDR5. DDR2 and DDR3 are especially flooded with weird brands you've never heard of before.
Unfortunately its not so cheap anymore as everyone ramped prices up of course.
Last year I could still get 32GB of DDR4 for under $60 from chinese brands.
DDR3 is from 10 years ago. DDR2 is from 15.