Products without prices

Is there a valid use case for a product without a price?
A price of $0 is valid, the rest is display logic.
Can this issue be closed?

Exactly.

I propone a valid use case.
I'm developing a web site where users discuss about some critical themes of our way of life. From discussion can born some Proposal of activity that users can do to focus the public opinion on the discussed theme. Each Proposal have some activities that user can reserve.
Activities Example: Post a minimal number of 1000 fliers and speack with a minimal 100 mayor of cities about the problem.
So each user that share the idea give the agreement to post x. fliers and speack with the 1 mayor of his city.
When the system detect that all condition are satisfied (several users have reserved together minumum of 1000 flier and 100 mayor) the discussion becam a Mission and all reserved user start with their action.

I'm looking for a system but I haven't found a specific module, sometingh like fundrising but our rising are not the money but the people activities. So is littele bit complex and a user can select more than one activities.

So I have think that If I use the commerce system each requested activities is a product with minimal amount (stock option). The cart became the user voluteer activities and the order became the offiacial agreement where the user say I make this.

In this system when a user create his product (with Auto Product Display and Commerce autoSKU) make his request and he don't want money but people agreement to make somenting.
Every time a user buy a quantity of activities done his agreement.

I'm also looking for somenting to create a personal currency (no money) but i've not found a solution.