Thank you for the replies so far.
I had in mind a specific scenario that could easily apply to either of our favourite low cost airlines.
i.e. on arrival at Stansted runway visibility is below allowed limits so a ROUTINE diversion is made to nearby Luton where the vis is within limits.
It is mid-evening so aircraft has not finished for the day.
Within, say, an half an hour weather improves - so is aircraft flown back to Stansted to continue scheduled next flight, although late, if that is what would happen. Crew still in hours, so far.
So extra distance flown,extra landing, extra take-off, more taxy, more landing/take off fees and ATC fees, more tyre wear.
How much fuel would this require? What would the extra maintenance cost be for the extra time aircraft was flown? Is the extra cost significant? How would this compare with the extra fuel usage for a 30 minute cross country taxy at, for example, Amsterdam or Madrid. Is it a big deal?
I have in mind like PPL training where each touch and go cost twenty quid and took 10 minutes off the 50 hour check.