Sorted mine by changing the bearings an a squirt of WD40. take the bearings out and take it down to your local bearing traders theres one in most big towns ! new set of bearings should cost less than a tenner.
£230 disgraceful. I was quoted about £50 by a Raymarine agent to supply a new wind direction sensor (you don't say if it's wind or speed you want, but I believe they are a similar price).
Obviously you need to go up the mast twice, but apart from that you only need common sense and ability to solder 3 (or is it 4) wires.
There's a good chance the WD40 suggestion will work. Might also find gunge on the shaft worked its way in from outside, should be able to winkle it out with a pin. That sorted it for me this year with the speed sensor.