Authorizing customers to see prices and "Add to cart" buttons
Create your private B2B store: Change your store to private B2B place and allow only verified customers to create an orders and see products prices.
Customers validation by admin: Approve or decline registered customers like you wish. Make sure they are good and suitable, before they can see products prices.
Hidden prices for visitors: For all not approved customers and visitors, you can hide products prices and "Add to cart" buttons and show custom message instead.