I think the general point of Samsung being the best choice for those on a tight budget still holds up in some cases, as discussed here. I don’t know where to find the best deals on used phones, but here’s a quick example. In Canada (prices also in CAD) you can get a new Samsung Galaxy A15 costing around $270 and I believe they provide security updates till December 2028. The next closest Pixel offering I could easily find was a (2 generations old) used Pixel 6a costing around $244 and is only set to provide security updates till July 2027. The used 6a is technically around $26 cheaper in upfront cost, but when you take into account the fact the new A15 will last an extra ~1.5 years in security updates and comes with official warranty, the new A15 is probably a better deal for most people.
If we make a fairer price comparison by purchasing a used Galaxy A15 at around $213, it’s even cheaper than the Pixel 6a. You might argue that these price differences are small, but for people who are financially struggling, having your device last an extra 1.5 years while costing even less than the competition might make a noticeable difference to their bank account. (I myself know people in situations where they can’t even afford that.) I probably didn’t find the best price for a used 6a, but I’d be surprised if you could find a 6a that is so cheap that it would beat out a used A15 when accounting for their security update support periods. Moreover, SecondCell supposedly offers 1-year warranty for their used devices, something you probably won’t get by finding a cheaper 6a someone is selling themselves.
It’s also worth mentioning that the new Samsung A16 that is just beginning to roll out may be far more appealing if Android Authority is to be trusted. According to their article, it should cost around the same as the A15 (or maybe a little more at the start) and will provide users with 6 years of security updates, lasting them till 2030.
To summarize: Older Pixel a-series devices could be a decent option for those who don’t have a lot of money. But at the same time, it’ll require that they purchase new phones more often as they may run out of security updates quicker, and that is probably not viable long-term unless they expect their financial situation to improve before then. In cases where people cannot afford to frequently purchase old Pixel a-series devices, getting the cheapest Galaxy A series device is probably their next best option. Everyone will have their own unique financial situation and threat model, and unless there actually is an abundance of much better deals on used Pixels that I failed to find, we should acknowledge the Galaxy A series as a non-ideal option.