Eurocontrol IFR clearance FO costs?
 

Didn't I hear that below 2 tonnes you pay nothing? There was a reason certain planes are derated to 1999 kg and I thought it was this.

Jan is correct - below 2Mt it's free. That's why some Senecas are artificially restricted by certificate.
Over that it is quite complicated because the calculation of charge depends on the country (FIR) being flown through, the distance between reporting points in that FIR and the square root of the weight (MTOW) ofthe aircraft. Hence the charges are biased towards the lower end of the weight scale and the big boys pay proportionally less. Eurocontrol used to have a software tool that you could download and work out the charges for any particular route; not sure if it is still there.
update - look for RSO distance tool. It's almost prehistoric but will tell you what you want to know (if you can make it work).

I guess that depends on your point of view. ATC has the same amount of work, regardless of whether it's a 2000 kg SEP or an A380. In fact, arguably ATC needs to spend proportionally more time with GA than with A380s, as GA generally flies slower and thus spends more time in a certain bit of airspace. However, the ATC charges are based on (the square root of) the MTOW, so the big boys pay significantly more for the same service.

Hopefully, this gives you a good idea:

https://cimg3.ibsrv.net/gimg/pprune....32b54480ec.png

"
... as flyingfemme points out if the charges are based on the square root of the MTOW then the big boys pay proportionally less."
less per aircraft, but more per hour?

I don't know anything about the flying side of things, but as an ATCO low and slow traffic around the London TMA is considerably more difficult to deal with as everything else is going a lot quicker and it's always in the way. We don't mind, as that's what we're here for, but our lives are far easier when it's a load of jets that are all doing very similar speeds. Our traffic prediction devices, for London area control, give each flight a complexity weighting as it goes through a sector and low and slows attract a higher complexity rating than a jet doing the same flight

Again like I said, we don't mind - I'm not having a go at anyone who wants to use the airways as they're there to be used - I was just saying in a slightly convoluted way that they're not the same amount of work.

It's done on distance, not time. The distance is worked out by using the great circle route from departure to FIR exit point then FIR entry point to destination/FIR exit point and so on So technically, the less time you spend in the airspace the more you're paying per hour :)