When looking for radio systems on ebay see Falco's post regarding counterfeit product. He is exactly right regarding pricing.
The next step is to work form the manufacturers pricing not from google searches. Most dealers will discount product on web sites, fair enough.
A radio system priced at £369 across the net and being sold for £199 on ebay is so obviously not the real thing. The RRP for such a product could be as high as £545. Use some common sense.
Sennheiser actually post the retail price lists on their web site.