But it is not free and having an open source app require fees for collaboration is problematic.
It is almost free to copy free software but the computer to run it on isn't free.
In the past I struggled with ways to price cloud services for 'data rich' applications that involved large databases. You wind up with different components of the cost: so long as the database is loaded into RAM and ready to query you have to pay for a server, maybe a big server. Some users are going to ask simple queries, others will ask complex queries that need more power. You don't want these people stomping on each other.
If you are Salesforce.com you charge a high price that lets you afford gold plated hardware with great performance and reliability. $75 a seat per month is cheap for a product that improves the productivity of a salesperson. Adobe's Creative Cloud is a bargain if you use it every day.
Products with lowball pricing are possible but a struggle to make work.