You can have a predefined price list just for a specific client. To create a price list, go to Contacts > Companies and find the company you need from the list or click on the "+" sign to add a new company.
When you select a company, click on the tab Price list.
Click on Create a price to add custom prices for this specific client.
Next time when you'll be creating a budget, you'll be able to add prices from this list by clicking on Add From Price List
