I had a Safari Books subscription for a little while, but I got rid of it. I can't remember the exact pricing, but IIRC it was around $250 / year for the cheap option that let me "borrow" 10 books a month. The problem for me was that I'd typically buy 2-3 books per year ($100-$150) and I owned more than 10 books total, so the subscription seemed like a bad deal by comparison. The "unlimited" (with limited downloads IIRC) was $500+ / year. That's a lot of books.
O'Reilly could have been the Spotify of tech books, but old school publishers were too scared to reassess their pricing. When the cost of distribution plummets, but results in a worse (ie: more expensive), product for your customers, it's not a shock to see those businesses struggle IMO, especially when the competition is free and "good enough".