You can easily tell the difference between a tap which uses a washer and one which has a cartridge. When a washered tap is turned on, the knob will rotate two or three times. A tap which uses a cartridge will only rotate 45 degrees (1/4 of a turn).
It it's a washered tap, mention has been made of replacement units, (often just a new washer is all that's needed), but if it's a cartridge type, replacements, known a 'ceramic tap glands', are ridiculously cheap, though when replacement are needed, the splined shaft must be the same height as the original. (Typically 8, 9, or 10mm) These for example, have a 9mm spline height:
https://www.toolstation.com/made4tr...&ranSiteID=pfxNKSnglIM-BEVqSy1WMZNwS.QQlyuaTA
Hope that helps.
Labour rates vary widely - in this neck of the woods an annual boiler service would be £75.00 and to replace a pair of tap tops would I guess be no more than £100, but most tradesmen live and work in the community they serve, only have a few miles between jobs, aren't beset with congestion charges, parking meters, traffic wardens and the like. On-street parking is unmetered and mostly not time limited, car parks are free in the village, (3Hrs parking in a multi-storey car park is £2.00, four hours £3.00, five hours £4.00). A 'traffic jam' is six cars at red traffic lights. A world away from the working conditions and operating costs for tradesmen where my son lives in Putney.