There are several ways you will want to set up product prices for one customer.
For example, the wholesale customer contacts you for a quote. And after some negotiation, you two seal a deal at a custom price.
Then, you can also create a rule for that customer so that he/she can add products at the agreed price and go straight to checkout.
Please follow steps to set up custom prices.
However, set Apply to Customers to Specific customers. Then, search to choose the customer(s). Multiple selections are allowed.
Also, if the chosen customer(s) has been assigned to two separate rules or more, the rule with the higher priority will be applied.
Besides setting up the custom prices for B2B/wholesale, you can also take advantage of the app for specific groups of customers, for example, VIP or birthday promotion, etc.