Most of the costs of an ERP actually lie in the implementation.
Implementing an ERP requires to do some configuration, which is what we are going to learn later on. It requires teaching users how to use it and how to organise their business with the ERP. It also requires sometimes to develop some custom scripts and interfaces so that the ERP matches the technical or business environment of the customer.
The total implementation cost of an ERP is usually estimated between 2 man days and 6 man days per employee in a company. This is usually equivalent to 1% to 3% of the company turnover or to 1,000 EUR to 3,000 EUR per employee.
If we translate these figures to a small company (6 people), we will find that implementing an ERP costs about 10,000 EUR in a small company or 20 man days. In a large organisation with 1,000 employees, an ERP will implementation will quickly reach 2,000 man days or 1,000,000 EUR. In a large multinational with 100,000 employees, an ERP implementation can quickly surpass 100,000 man days and 100,000,000 EUR.
At the same time, the cost of selling an ERP, which is mostly the time spent in convincing prospects to adopt a given ERP, does not change so much between a small company and a mid size company.
As a result, ERPs are not used very often by small companies, only because nobody is willing to spend time convincing them to adopt them and make no profit out that.