The 0800 Number Company takes a different slant on 0800 numbers in this blog post.
Most marketers recognise the power of 0800 numbers because they are free to call from a BT standard landline. For this reason alone it is easy to see why 0800 numbers are seen as "income generators". Why pay something for the cost of a phone call when you could pay nothing?
However The 0800 Number Company also sees 0800 numbers as "profit generators".