Commercial ERP is an expensive package and suitable only for bigger corporations. The prices do vary significantly but according to the size of the company and volume of business.
The time allotted for implementing open source ERP is very less when compared with commercial ERP than open source. The innumerable number of complexions in commercial ERP calls for longer time span. It consumes a lot of time not only during implementation but in every stage of ERP process due to the nature of work involved