Tech Question – B2B Software Subscription Pricing

For all the tech IB/PE/VC monkeys – When looking at valuing tech companies that are based off of subscription models, like B2B software companies such as Salesforce, how do you validate their pricing strategies/models? Do you look purely at what their competitors are charging / would charge? Also, how would you validate sales volume? Look at historical revenue and forecasts for the industry? Ex. – If a company says they're going to sell licenses for $1mm/year and 100,000 licenses a year, how would you find external support?