Joomla and Mambo CMS have been developed by the same professionals of web design industry. So, they possess a lot of common features. For example similar code, system requirements, etc. At the same time new releases of Joomla will differ from Mambo. Having compared Joomla and Mambo CMS‘s you can notice that Joomla has more options, better security issues, regular updates, additional Built-in-Applications, etc.
When you hire a professional web developer to make a website for you, it is also going to cost way more money. There are low-priced developers, and then there are high-priced developers. But no matter what you are going to end up paying way more than what you expect. Each one comes with pros and cons. Low-priced website designers are not going to be that experienced, but that is why their prices are going to be so low. This does not mean that they do not have the skills; they just are not proven enough yet to warrant a high price.