When I used the free trial, the main activity was centered around pasting text from other sources/sites, then marking the words you recognize. To me that's not worth $8/mo, much less $40 at the Premium Plus level. I realize there are a few other features to LingQ but the cost-benefit of the lowest tier didn't make sense to me.
I have free dictionary apps that remember every word that is looked up. I'd rather input those lists into a spaced repetition app and receive essentially the same benefit without paying.