FWIW, "tier 1 ISP" is less prestigious than you'd think. Many tier 2's are bigger than many tier 1's. Being a tier 1 is kind of a self-exclusionary, nose-snubbing policy and in some ways it's surprising they manage to hang onto existence at all, though not in all ways.

This typically comes up when someone thinks they're getting better transit service from a tier-1 than a tier-2. They're not. A tier-2 ISP can have better routes, since a tier-1 will refuse to deliver your traffic anywhere that requires them to pay money. Some places are just unreachable from tier-1 ISPs.

Famously, for over a decade Cogent has refused to receive packets from Hurricane Electric without payment because idk profits, and Hurricane Electric has refused to pay them because it's a tier-1-ish, so you just can't talk to Cogent customers if you're an HE customer and vice versa. (I think HE eventually relented by paying a third-party to forward packets to specifically Cogent, even though they have tier-1 status to everywhere else)