And then there were the software licences and cost to develop software. As a rule of thumb you could calculate those like: PC (1) - minis like e.g. AS400 (mult

And then there were the software licences and cost to develop software. As a rule of thumb you could calculate those like: PC (1) - minis like e.g. AS400 (multiply by 10-50) - mainframe (multiply by 100+). For example in the early days of MS there was an MS Excel running on IBM mainframes - US$200K per license and per year. To top that when IBM, DEC e.a. where among the few providing such computing power (into the 1980s) and those companies that required such bang on a broad scale - banks, insurances, research institutions but particular banks with their need for many workstations as well - IBM did framework contracts forcing their mainframe customers to also buy their PCs as workstations often for many years. That was one of the reasons why you found all those very expensive IBM PCs in banks - tens of thousand in each of the larger banks - while you could already buy no-name PCs for a fraction of the price. (A fully equipped PS/2 could easily cost the price of a small car and for development machines you could get up to a Mercedes S-class entry level price - by now prices of the PCs dropped to a fraction while the prices of the cars multiplied by 3-5) An interesting example of how monopolies / oligopolies are created / kept alive / and it still takes many years in markets moving as fast as the IT industry until they die or loose the grip on their customers.