I think you have answered your question. If your customers are telling you "adding content is time-consuming" you should ONLY be focusing on solving THIS particular problem.
"Should I increase my prices?" is a "vanity question" ( just like "vanity metrics" (E Ries Lean startup philosophy) >> They do not help you build a better business, they take you away from what is REALLY important) Finding why your customer do not want to spend more time adding content and/or why they consider spending more time adding content is not worth it definitely help.
You are in the language learning industry. In learning, pratice is key. Learning is a journey (takes a some/lot of time).
(expertise is 10 000 hours of work/experience)
What is good about learning is there are levels (ie. beginner, intermediate, advanced). For the software/app maker, it means there are different needs to answer. For your potential user, it may mean, there is a potential long term gratification "I am a beginner user today, and tommorrow I can become an advanced user". "I can make progress."
- How to make your visitors sin up ?
Break down the different japanese apprenticeship levels. Show your user, examples of instant gratification. Even if they are beginner, they can get something.
- How to make your users stay and use your app ?
Gratification at every little step they make. ie. Every time they write a good answer.
In other words, I think adding a layer of gamification would be interesting for you. It would spark your visitors interest, grow your user's engagement.
- How to make people come ?
Maybe by allowing your users to challenge their friends. Ervery time your user reach a milestone, allow him to post on Twitter/Facebook something like this : "In two weeks, I allready completed X,Y,Z levels of Japanese. What about you ?" (far from perfect, but you get the point).
Having a freemium business model is a good idea. It lowers the barrier entry for the user.
In addition to that:
- Define the the user tipping point : when are they addicted. What does it means to be addicted to your app.
- Define the right metrics to analyze.
Many startups in the learning industry have successfully implemented a gamification layer in their application.
You may take a look at codecademy.com and veri.com
"Should I increase my prices?" is a "vanity question" ( just like "vanity metrics" (E Ries Lean startup philosophy) >> They do not help you build a better business, they take you away from what is REALLY important) Finding why your customer do not want to spend more time adding content and/or why they consider spending more time adding content is not worth it definitely help.
Good luck.