Bearing suppliers can provide bearings very cheaply if your in the trade but then you can get as much as a 70% discount, but if you have a price of OE if their cheaper you will know.
Not quite sure what you are trying to say. Bearing services don't usually deal with the public, but if you phone up or turn up at their counter they will generally serve you. And as they don't generally deal with the public, well, as far as I am aware, there ain't no trade and retail prices, just one price. Sure they will discount a wee bit for big contracts.
OE I take to mean original equipment if so I can not see the likes of Yamaha needing to fit sub standard bearings, other cheap after market bearings I would be wary of.
Yes OE means Original Equipment, as in what the bike comes with. I never said that Yamaha fit sub standard bearings, but they will fit the cheapest option that will do the job.
The wheel bearings fitted to your bike will usually have a multitude of industrial applications. In the power station in which I work we use loads of these types of bearings in a variety of different applications. A good industrial electrician or mechanical fitter will understand the codes or refer to their guides to determine correct bearing selection. There can be quite a few different options for one basic type of bearing, plus a quite a few manufactueres. Most of the stuff I see is SKF.
A simple upgrade to better seals and a high tolerance unit over the one fitted to the bike will cost you buttons at the bearing factor, the guy at the counter should quickly determine the best option for your application (assuming you have the bearing code).
There's a thread in the thou section, BMCfaz got a quote for the OE chain and sprockets kit, it was 568.89 quid. I wouldn't bother asking a Yamaha dealer about bearings, just get a set of best quality SKF from the bearing factor for buttons.
If you wanna read up on bearing selection;
http://www.skf.com/portal/skf/home/products?maincatalogue=1&lang=en&newlink=1_0_50