Hey Adam,
You can't do this. However there is a possible alternative. It depends how you are going to solve this. Are you going to charge people just once for the right to submit events, or are you going to charge them every time?
If you are going to charge them just once per year or month for example (like flat rate), then you could do this with a subscription extension. For example on our site we use akeebasubs (which is a developer product, right now) what it does is once you buy a subscription -> it ads you to a specific joomla user group. This user group then has the right to download the extensions and submit tickets. Once a year past by akeebasubs removes this user group from your profile (it downgrades you). So if you are going to do something similar - you could find a subscription extension that would add the user to specific user group, which is able to create events.
If however you are going to charge per event, then you could still do this with a subscription extension, but it would also need an integration with matukio. Maybe with a plugin. So when a user posts an event, we would have to calculate how many events this user has and then remove him from that group if he has reached some kind of limit. But now that I think of this it won't work as the user won't be able to manage his own events one he is removed from the user group.
I think that you would need some custom development for this. If you want us to give you a quote use the form here:
compojoom.com/services/joomla-development
Regards,
Daniel
