Wondering whether a new dmm cheaper than calibration cost? I've no idea.
Calibration is likely to cost £20 to £50 depending on what the device is.
It's necessary if you are using a meter professionally and submitting test readings to a client or building control.
For an amateur, I very much doubt it.
The best value way is to cross check your meter against another if the opportunity crops up. Either a friends or a second one of your own that might not cost much more than a single calibration fee.
Folk who do much electrical work may find a second different meter handy.
e.g.
Clamp meters are incredibly useful for measuring current without having to wire the meter into the circuit.
Specialist "leakage clamps" are sensitive enough to measure the small currents that trip an RCD and are useful in fault finding modern domestic wiring. "Nuisance trips" are pretty common now that RCD use is widespread.
Electronics nerds might need a (typically more expensive) 5 digit high resolution meter and a super sensitive micro amp current range for work on circuit boards.
All of these will also, usually, have some standard volt /amp / ohm ranges so they can be used to sanity check each other.
Incidentally - you can get current clamps as an accessory that plug into any multi meter. The accessory style aren't sensitive enough for measuring RCD leakage currents but for measuring the current being drawn by a machine or motor, say, they are handy. You just clip the clamp around ONE of the live or the neutral wires.