Those drawings would have to be designed to go with the theme of the website, it would probably be a few hours work just for those and then a top end website would cost a lot again.
There are cheaper companies that just have a few website templates that they use and then just customise them with your logos and information. But the better companies are ones that design from scratch.
If you're paying a proper professional design company, not just a bedroom designer, the prices will be high, especially if they have an office/studio to pay for and employees.
Have you shopped around for quotes?
Here's a designer friend of mine based in Yorkshire, try contacting him for a quote.
http://www.uc48.net/