One of the annoying worries is the possibility of an airline asking for “proof of onward travel” before checking you into your flight. Airlines do this theoretically because they may be liable for getting you back out of the country. Airlines also check that you have a visa for the new country for this reason (which also confirms you have a passport).
It makes sense that they check that you have a passport with a visa for the destination. Still you could be rejected from entering even with the visa. If that happened I don’t see what good it would do to have a plan reservation in 50 days going somewhere. I suppose the country might push the responsibility for getting you out of the country to your departing airline but I seriously doubt it. If you claim you can pay to leave I would have to imagine if some other party gets stuck with the bill it is likely the airline that delivered you.
I suppose it could also be the airline only gets stuck if you don’t have proof of onward travel. And if you have that proof they are still responsible for getting you back but someone else pays until someone can collect the money from you (and gets stuck with it if you never pay). This seems pretty unlikely for most “normal” travelers from rich countries that have credit cards which would just be billed for whatever cost there is.
It sure seems to me that credit cards should add a perk to “gold cards” (or even less fancy card types) that promise to bill whatever costs accrue due to you being forced out of the country to you (and just like other costs the credit card issuer is stuck paying the cost if you don’t pay them back).