It took me about a minute before I was prompted to create an account and another minute before I was prompted to sign up for a subscription. I'd gotten through about 4 sentences in total (I clicked a fair bit since I'm still learning the language).

I'd happily pay $4 a month / $30 a year. I really like the Chrome extension as well. Here are some of the features I'd thought of adding to my (now cancelled) project:

Being able to see the meaning and usages of a word with a hover of some sort. I find it annoying to keep clicking on the right hand side to pull up the definition. Additionally, a number of definitions are just not available.

Something I find myself doing a lot is selecting and trying to right click. The 8 word limit on phrases means I'm stuck with typing stuff into Google Translate. For longer sentences context gets lost and so the translations are not accurate.

Being able to collect personal word lists. This is great for learning which is my primary intended use.

Keep in mind that I'm a beginner and the requirements of someone at an intermediate level might be very different.

Hope this helps and I'm looking forward to using it even more!