I already had a pair of KSC75, bought a few years ago from Amazon UK. I like the sound and the comfort and convenience, especially when paired with the Parts Express headband. I bought this Massdrop version as a spare as I do sometimes lose or break stuff. Koss prices here in UK have risen between 50% and 100% over the last decade (I assume this correlates to Amazon killing almost all online competitors for retail consumer electronics) so it is now as cheap, or cheaper, to buy from abroad and pay shipping. That's why I bought these from Massdrop instead of a UK based online retailer.
They are very nice earphones. I have some great In Ear Monitors from Shure (SE215, SE425) and Vsonic (GR07 BE) and some great closed back headphones from Sennheiser (Momentum circumaural v1) but sometimes at home I want to use headphones without becoming totally aurally isolated. The Koss KSC75s are pretty much ideal. I also love the Porta Pro, which is probably more familiar to many. The KSC75 has a less exaggerated upper bass, resulting in a more transparent midrange. It also has more extended and airy and sparkly highs. I can see why some might prefer one over the other, but I like and use and enjoy both Koss models according to whim.
In terms of design/manufacture the weak point of this range of Koss products is that, like most headphones with fixed cable, the cable can fail at the driver end if it gets tugged or snagged too often. The cheap looking jack on the original is actually just fine, and the Massdrop version seems good too. Fortunately these are incredibly easy to disassemble and even a clumsy person with two left hands (me) was able to solder a new cable when I broke my old pair. You can buy a ready made cable on ebay or aliexpress, almost for pennies, that just needs soldering.
I'd recommend these to anyone, they have a beautiful and natural sound, and are very comfortable.