I've just built something similar for a Auditing company, who survey sites and have to produce a report based on their findings with SVG graphics and PDF output, retaining all the data for each company and providing a profile/login for each.
Its pretty complex for a relatively simple idea, and took about 6 weeks to fine tune and get working with all the features they wanted.
£499 wouldnt even come close to the time spent on it to make it financially viable.
Really you should be looking at between £2500 upwards into the 10-15k range for custom platforms and software.
As they say a "cheap customer", is an expensive customer! Cheap often takes excessive time for the money you're getting, and more often than not will be much more demanding than someone who understands the time and support these things need.
