Sounds like you need a tiered pricing and quantity discount app. We have a list of the best Shopify tiered pricing and quantity discount apps, hope that it will give you some suggestions.
I have similar question but the only thing is I dont see much of an app which distinguishes both the groups. There are wholesaler support apps but something which will allow B2B guys an access for other products and special pricing. Again as said , B2C customer should not be able to get directly to see the wholesaler support prices as well. Anything of this sort ?