Nice job! You should limit that $6 a month based on the # of blocks. I could see some more "enterprise" type customers using this and you'd want a way to push them in to a much higher price point.
I see your point and agree with your assessment. I simply decided to release it early to get feedback and squash bugs, hence the single discounted plan.
I do plan on having at least two tiers and yearly subscriptions once the product matures.