Repeat revenue makes it easier for me to make a living as an indie dev, so I wanted to give this model a try while charging what I think is a fair price. I'll keep an open mind about it and adjust if enough people want it. Appreciate the feedback!
Of course it does! "And a pony."
You have to realize that most people are exceptionally leery of subscriptions as they are open-ended long-term commercial relationships with some random entity. There gotta be rock-solid clear benefits for a subscription to be justified. There are none in your case. What you have is a product, not a service. A subscription makes no sense whatsoever.
With regards to the fixed pricing - 3000 word pack is not the best option. What's more useful from the language learners perspective are packs that cover specific domain area - foods, kitchen utensils, car parts, body parts, weather elements, household tools, etc.
"3000 words" = "Unclear what you are getting"
"100 words, Garage" = "I may be able talk to the mechanic"
If you have smaller packs, you can sell them at few bucks a piece. You can try and experiment with discounted bundles of packs. And you can also try an all-you-can-eat option with a monthly access (yes, subscription), but as one of the options, not the only one.
PS. Have an option of switching off photos on cards.
Buying the language a few hundred words at a time won't get you to fluency as quickly as learning words by frequency until you have covered the most frequent ~80%. Only then does it make sense to focus on specific domains that are most interesting to you.
For example, I am learning German. I would rather have a pack with the 25 most frequent nouns, 25 most frequent verbs, and maybe 25 most frequent adjectives. Then I have a foundation of vocabulary to learn the dativ and akkusativ. I don't need the adverbs yet.
Also, if I'm learning the modal verbs, I'd like a pack of those.
I just think that's interesting in the context of your use here.