Just at the moment one could expect the monthly lease on B737’s ( with 148 seats ) to be in these ranges:
737-300 = $135,000 to $180,000
737-700 = $190,000 to $270,000
That said, –700’s are hard to get hold of (hence why it can command a higher monthly rate).
Of course on top of the basic lease costs, you also got the following to consider as well:
Hull & engine insurance
Fuel charges
Aircraft & engine maintenance reserve payments
Contingency funds
Navigation & EuroControl charges
Airport approach, landing, handling, and parking charges
Pax taxes ( indirectly )
Crew training costs
Staff salaries
Office rentals
IT/Systems
Company vehicles
Etc, etc, etc.......
Now if you lump the whole lot together, I believe that you’d find that the ball-park figure for operating a B737 ( for a typical UK charter / low cost airline – with an aircraft operating, say, 4000’ish hours per year ) is something in the range of £60 to £100 per MINUTE !
..... and somehow you’ve got to make a profit within that lot too !