It's what I happen to bump into. I pick used games from flea markets for 1-3€, 4€ is the absolute top unless it's something I specifically want or a collection.
I actually keep a list (as I have habit to do in many things), so let's see how many games I've bought each year. (Both collections and expansions as separate product count as one; essentially how many pieces I bought rather than number of actual games. Games that don't run included, whether it's due my hardware or scratched disc. Some games I got for free may slip in.)
2023: 18
2022: 6
2021: 10
2020: 15
2019: 20
2018: 9
2017: 10
2016: 7
2015: 12
2014: 4
2013: 0
2012: 8
2011: 16
2010: 4
I think 2012 or 2013 the place next door that had been my primary source of games since it opened 1997 shut down. On the other hand 2014 or 2015 opened the place that is my current hunting ground, as well as another small one.
2019 I got my cousin's old PS2 so I started buying games also for that. Last year I was introduced to yet another place where I do not expect to get much from in future but happened to have a pile of junk for peanuts.
Typical pace seems to be about a game a month, though I usually buy more than one game at once, so it's more like couple game every couple months.