You can argue the risk comparison between an old airbag and no airbag, but the thing that sways me is, beyond a certain point, the manufacturer just doesn't care if it works or not. When 95% of the cars have been scrapped, nobody cares if it doesn't work right anymore.
I also consider that on an old car without an airbag, I still have a seatbelt that I will wear, and on an old car with an airbag, I still don't have modern crumple zones and reinforcements.
So I'm sticking with either relatively new vehicles or pre-airbag ones.
$275/month is $3300pa, so you're already at a minimum of $6600 for a near 20 year old car, which doesn't sound particularly cheap.
I'm on a lower monthly cost of ownership for 3 years ownership of a 6 year old car.
Also, it's not a car - it's an SUV - so it's going to cost more than a car. I bought it because I really wanted an old 4Runner, not because I wanted the cheapest car.
Your mention of costs seemed to imply that it was cheap which didn't seem to me to be the case.
However, anecdote vs data:
"Used car payments hit record $400 per month as prices top $20,000" [0]
So I still think I've done pretty good with my purchase.
[0] https://www.usatoday.com/story/money/cars/2018/11/08/used-ca...
Sale price plus maintenance divided by time owning it currently has me at $275/month and dropping.