I don't know if you're missing the point of the original advice on purpose or if you're just in it for some sake of a social circle frugality. Regardless, please let me take advice from your verbosity and make it absolutely clear with my intention.

The point of the original post was that the money you save buying the cheapest alternative of the comparable range of product you have isolated as an appropriate solution for your predicament is likely a bad investment, for if it is priced way below the median - without being on a fire sale or some other reasonable circumstance - the shaving off the price must be in the production, be it in quality of said product or exploitation of producers, as there is always a price down the line, be it monetary from your own pocket for an early replacement product, or the collective cost of making life a little bit worse for somebody else on the other side of the globe. Agreed, the latter may or may not be of consequence for the subject.

The point in the follow up addresses that if you compare single instances relativistically across classes, you have no frame of reference if any of your selected candidates are of preferred cost/quality as there is no singular frame of reference. This implies a preliminary step of filtration of the range of products to compare, the very one that you're showing through an example.

My advice is regarding the step following the iterative process of analysis and selection. That is, we've compared either shoes, bicycle, car, bus ticket, hitch hiking or levitation and have decided that the class of shoes will do the trick.

We now need to assemble a selection of candidates from our previously decided class of solution. And to complicate even more, shoes as well come in different types and ranges! A pair of hiking boots? Genuine Italian leather shoes? A pair of flip flops? Can we already apply the rule of thumb to not trust the cheapest option? Oh, let us not be hasty. Flip flops may well serve our needs, should we have good feet and our commute is short and vacant and we reside in a hot climate. If, though, we live in norse climate, other types of shoes may be more appropriate to trod through snow and water and ice and general grimness. I'll leave it for the imagination to decide the subclass of shoes to be decided upon, personal preferences and all that, which shall not hinder the flow of this narrative.

It is now and only at this stage, now when we have already narrowed down from class to subclass to segment and subsegment and filtered out marked up brands and price ranges that are beyond our scope. Now that we have a handful of viable items of which we shall decide upon one pair of actual physical shoes we shall wear for this season and hopefully many more to come, it is now and only now that we can apply this final filter.

Our hypothetical selection has one pair of a highly reputable brand that are nearly four hundred money, but are whispered in the shadows to last a lifetime if not many. The middle section of a hundred to two hundred money a pair of branded shoes that all seem fair, and in the bottom end that one pair that caught our eye that are fifty money at full price with a brand name we've never seen before and can not find a single hint that they might be a snazzy eco friendly high ergonomy fair trade product that is breaking in on the market at a provocatively disruptive price point. Unfortunately, they are but an unknown pair of footwear at a tempting low price.

It is at this point we can apply the wisdom I wish to bring forth.

If the median is somewhere around one hundred and fifty money for a pair of shoes that fill our preset requirements, my words are that it is recommended to take in consideration why the price of both these outlier shoes are at such difference from the others in our list, and to make an informed decision based upon parameters other than the numbers on the price tag, for it may well be a deception with the savings of the lowest immediate cost as the difference may well present also the difference in quality, and likewise the expense for the top end may keep our feet dry and comfy for winters upon generations to come.

Yes, it is here that I wish to inject these words to remember.

What is cheapest, is always the cheapest for a reason. There is always a reason. Always. And in a market economy it's rarely a good reason, except maybe in the short term for the monetary receiving end of the transaction. There may be the rare exception, but it will never be a bad advice to consider it for whatever purchase you make that is of some hint of significance.