It’s really striking how much of a difference there is between free, and even a penny, especially when that is a recurring charge. For me at least, if I have to pay for something it must have demonstrated value (either via demo, or other users, or a free tier). Only then will I consider the mental overhead of managing yet another subscription. That is to say nothing of the actual cost.
This idea specifically doesn’t make sense. Why are contributors the ones who are paying? Shouldn’t it be advertisers, employers, and “sponsors” who foot the bill?
Creating a contributor account should be free. From there, active contribution should be rewarded in some way. Those looking to capitalize on the contribution of others should pay. Think bounties, sponsorships (project or individual), or even Mechanical Turk like tasks.
You still have to overcome the existing competition in this space.