I have seen situations where it's hard to justify bespoke software over free, open source software, especially to a computer illiterate person. Some open source software is really good and definitely as good as it's commercial competitors and some (*cough* osCommerce) is a big pile of donkey poo.
Taking osCommerce as an example, the customer doesn't care that it's a big mess of code that follows no decent structure and has been held together with spittle and sour milk, they just care that it does what they want and it's free (and therefore all they should be paying you for is implementing it).
Taking osCommerce as an example, the customer doesn't care that it's a big mess of code that follows no decent structure and has been held together with spittle and sour milk, they just care that it does what they want and it's free (and therefore all they should be paying you for is implementing it).