Packages are always very expensive this far in advance. TUI flight-only is also expensive because on the whole I think they prefer to sell packages. The hotel owners don't get that much apart from a big on-line marketing operation, so what looks like a cheap holiday is actually a fairly dear flight.
It's a lot easier to have your own servicing and maintenance centre at a large airport. Smaller regionals can never be as cheap as Manchester or Stansted. We pay a bit more for the convenience.
Fuel cost rises are significant. A typical TUI or Ryanair 737 fuel cost was about $1500 per hour in 2020. So, about $9,000 to fly to Corfu and back from the UK. That's heading towards double already this year, so say around $15,000. A 737 holds up to about 200 passengers so a full plane = $75 per passenger. Add the cost of the plane and crew, and you're not making money. But you can carry cargo and get paid for it. Cargo is better at bigger airports, or airports with good transport connections. Doncaster is a big cargo hub. Wizz Air flies from former eastern European countries all year round. It's very near the M18/M1/A1M motorways. Fly your Greek yoghurt on a TUI plane from Corfu, load it onto a WA jet, and it's in Bucharest in a few hours.