how on earth do they justify a £90 RRP? (Cost me £25 BTW).
Just because you paid £25 on Ebay doesn't mean that anyone selling at the RRP is making £70 plus out of a product. The RRP assumes a convential supply chain (manufacturer – national distributor – LBS) and enough of a mark up at each stage for an honest living to be made.
There are various reasons stuff appears cheap on Ebay or other sources.
Surplus original equipment being cleared out,
Obsolete or superceded stock,
Bankrupt stock,
Stolen goods,
or as mentioned above Fake Goods