craigslist sometimes has bulk sales. E.g. there was a guy in LA, a few weeks ago selling 1000s for $5 a piece, incredible selection. There are a lot of collections up for sale, some only sell to one buyer, some willing to sell one by one.
I go to a record store once a week and buy from ebay. I always have a plan, look for a certain artist and go for the lowest price. Worst case scenario I buy it again, I'd spend 5-10 dollars twice rather than 35.
For some albums, new may be best, you would need to know about the specific copy, who/when/where, I had a post about that with great insight provided in the comments.
I have three new LPs in the original wrap, I have not opened them. I just look at them from time to time and feel like I need the right moment to remove the nylon. For me vinyl is all about the time travel and I want that original sleeve with the 70s ads on it.