Well, they do say that modern capitalist production is partly predicated on the concept of 'inbuilt obsolescence'. Actually, I still remember my shock when my Professor of Political Philosophy explained this concept to me quite a few years ago.
Having said that, some products still last well, but the other old adage applies, namely that - to a certain extent - you get what you pay for.
Personally, I use Bowers&Wilkins headphones and find them superb. I have had my P5s (granted, the drivers and leather was replaced once) since 2011, and absolutely love them.
Funny, and true...
I studied civil and industrial engineering, with minors in environmental engineering - and marketing. In that marketing, we were taught several "models" of success, and failure - of which one describes your professor's teachings in this regard, IMHO.
The ideal, perfect model was created years ago by Proctor & Gamble - adding the word "Repeat." to the end of the "Apply. Lather. Rinse." instructions for shampoo, about doubling consumption with the addition of one word to their labeling.
A successful business model is that used by many automotive manufacturers, especially back in the 50s/60s by Ford/GM. Sell a solid product, then upsell and provide accessories and branded consumables (like windshield wipers).
Then, there's the "fatal" implementation of an enterprise resource planning model by Tektronix - I've used their oscilloscopes. They built a bulletproof product, saturated the market - then died when they sold a product that never really needed servicing to everyone in their target market. I'd bet those scopes and meters I used in college 25 years ago still work flawlessly...
I like Grado Labs' approach - build better drivers, tweak the model number (SR125/SR125i/SR125is/SR125e), distribute to tech/music rags so the ad budget is kept low, and make sure everybody sells at the "retail price".