Drug firms desire maximum profit, subject to not taking on too much political risk, and will charge different prices dependent on the wealth of each country.
Countries may require that drug firms divert most vaccine doses to public sector hospitals... with only a bit left over for the private sector. A person in Switzerland will likely be willing and able to pay a higher price than a person in Somalia. I suspect that many of the wealthier people in the world (ie anyone earning more than maybe £50k per year) and large corporations will pay handsomely to be able to show a vaccine certificate without waiting 6 months while the pensioners are processed
There is a high correlation between a country's wealth and its propensity to buy air tickets. The aviation industry will likely be content to let economics to run its course