I wear mechanix wear gloves instead of the dive gloves that don't last. I wear chuck taylors instead of much more expensive dive boots that aren't as comfortable or any better performing. The webbing that is on my harness doesn't have a name brand.
The parts that go in my gas supply, will have a name brand that I trust and respect. If all parts were truly created equal, I don't think that we would buy apeks or scuba pro regs to begin with.
The real issue here is how much difference in price compared to the difference in quality (if any).
I would argue that a K to DIN converter may be twice the price for the name brand over a generic however there is not twice the quality difference or even 10% more difference. We have been conditioned to think if its twice the price, it must be much better, therefor worth the extra. A good marketing ploy, however quite often not of much substance.
That's not to say that the $5 special will meet all the requirements for use. I try and buy mid price which is an affordable item and yet has reasonable functionality and quality.
The old saying "A fool and their money are soon parted" seems appropriate here.
I see kids walking around with $200-$400 sun glasses, and yet I wear $25-$40. I would defy anyone to tell me how the quality can be 10x better for the higher priced glasses.
In the main it would seem to me that the majority of manufactured diving products are of sufficient quality to meet reasonable industry standards. There are always a few dodgy ones, but most are reasonable. I have mid priced regs worth about $190 each, and a mate has $600 top of the range. Yes his breath lighter, but in my opinion they are not worth 3 times the price. The cost to manufacture is similar but they are 3 times the price. They may be 10-20% better?
Some people like to have bragging rights and love demonstrating how good a diver they are by the price tag on their gear. For me the proof is in the eating of the pudding, not the buying of it. Show me their skills as proof not a price tag, one cannot buy skill and ability. They might look s*^t hot when they gear up, but still look the fool in the water when they flail around like a drowning rat.