We recently had a thread on a similar subject a couple of months ago here:
http://www.scale-models.co.uk/showth...hlight=proxxon
I think you get what you pay for as regards quality so you have to decide, based on your own use, what you think it is worth to you. Usually cheap stuff will do the job but not for very long!!
I once bought a very cheap and nasty circular saw from B&Q specifically to do a laying of a wooden floor in the dining room. I didn't have any other use for the saw and it did the one job perfectly. If I was doing the same job every day the saw wouldn't have lasted very long but it was perfect for my use. If I throw it away it was still an economical decision.