As one who thought your question on ear-plugs was off-topic, as a shopping and not travel question, I would like to offer my opinion on the other shopping questions.
Yes, I believe most of the other shopping questions are also off-topic and should be closed. But not all of them. And yes, I know in my comment on your Q&A I said that most were on-topic, but after you responded with some links I took a deeper look and now have changed my view.
I think allowing them has opened the door to questions like (using the example I commented on your question)
I'm currently visiting Tijuana and need tyres for my car before I drive to San Francisco. Where in Tijuana can I buy
good-quality, American known brand, tyres and have them fitted to my vehicle?
Now clearly (at least to me) this is not a Travel question, it's a shopping question. But I use my vehicle for travel, and I'm about to take a long trip in said vehicle, so maybe it's on-topic. No, I don't believe so
And I would argue that most of the shopping questions are similar to this. User has traveled somewhere and now wants to buy something. The buying has nothing to do with the traveling, so it's a shopping question not a travel question.
That all said, I believe that there are some that are on-topic. From the four linked in the question, I would vote for Does Estonia have discount supermarket chains like Aldi and Lidl? to remain open. This, to me, is a question asked by a traveler about what to expect when they arrive, and makes it more on-topic than most of the answers.
I think we should expand the existing Close reason to cover off-topic shopping questions, not just price shopping. Something like
Questions on shopping for specific goods or services are off-topic as
prices and availability change frequently in many locations. Questions
on where to buy items or who to buy from are off-topic as these are
not travel related.
(OK so that needs work...)
See also What is a shopping question? (which is, in fact, linked from our existing Price Shopping close reason)
Now, could my Tijuana tyres example, and your ear-plugs question be adjusted to be more on-topic? Yes, probably...
I'm currently visiting Tijuana and need tyres for my car before I
drive to San Francisco. I'm sure there are tyre shops in the city, I
just don't know what I'm looking for. What do I need to look for to
find "tyre shop" in Tijuana?
which could potentially be answered with something like:
A tyre shop in Tijuana is known as a Llantera - there are many
around, just look for signs with the word Llantera and you'll be in
the right place. Or ask a local for directions to the nearest
llantera (the ll makes a kind of y sound)