Wholesale products

Well, it's probably not something easily detailed here in terms of precise direction, but it sounds like you are only speaking of a couple "display only" places where this would appear.  If you are comfortable with code, it's not going to be exactly rocket science to dig into the code and make the adjustments to do what you are asking so long as you are careful not to interfere with other functionality.

No not at all.  Just create the wholesale categories and then click on the link add products.  They can be shown in both retail and wholesale categories with the same sku. 
Katharina

By default you will see the retail category before login.  After login the retail customer will still only see the retail category.  The wholesale customer will see both after login.  Below in a table format.
No login:
retail customer - retail categories
wholesale customer - retail categories
After login:
retail customer - retail categories
wholesale customer - retail and wholesale categories

So there is no way of hiding the retail categories to the wholesale customer.  But that is not the point I think.  I think the idea is to have a clean look to the wholesale customer without having to weed through products.  For that it will work well.
Katharina

Hi, Harmish.  It would be foulish to hide the retail pricing form the wholesale customer.  They will find your prices anyway.  The point is for example you have 10,000 products, but only 500 have wholesale pricing.  (I think that was what the original poster was after.)  It would be hard for the wholesale customer to weed through them to find wholesale products.  Creating a category that is only visible to wholesalers after loggin, as I've said before, is the best solution.  That is currently in place.  I simply had the suggestion to perhaps enhance this a step further to give more options to the category, by offering to show categories to wholesale, retail, or both.  You are right with the question what to show to those not logged in.  My answer would be retail.  Perhaps something to be set in the store settings.
Katharina

Hi Katharina,
   The big issue here is - What is someone who is not logged in?
I can't really see any alternative than treating them as a retail customer at that point. It's certainly possible, with a fairly small amount of customisation, to hide retail products from wholesale customers AFTER they have logged in, but until that point there is no way of distinguishing them from the rest of the customers, they are just an anonymous surfer like everyone else.

One option is to run a separate site, or a sub-site, which requires login and is dedicated to your wholesale customers only. I believe you can run off the same DB, but I've never done this myself. 
If you set up the website navigation in a suitable manner it's  possible to guide your wholesale customers to  sign-in at the very beginning to visit the wholesale side of the store, but I very much doubt it's possible to prevent them seeing your retail store. 
An analogy is a physical store. Any store open to the public is, by it's very nature, open to everyone, wholesale clients, rivals, anyone. 
Some physical stores are "Trade Only" and you need membership to access them. Some companies operate both types, but often do so under different brand names.

On PC as it stands, what wholesale customers DO SEE is the difference in price that they are getting from retail customers (if the product has a retail price), for example :-