Durability of any part - both mechanical and electrical - can usually be calculated down to a very precise margin.
Not an electrical engineer, but for bearings at least it's basically a 101-class thing to calculate their lifetime.
Down to thousands of hours exact...
Though usually parts are rarely the price issue, manufacturing tight tolerances is (for example, shafts for washers in theory have to be produced to a very tight tolerance spec for the seals protecting the bearings to last).
Manhours are expensive aswell, so software testing is often cut short (thus the many glitches in PCBs).
And it usually isn't that terribly much cheaper to build something less durable.
Reason they can cut margins short and make products cheap is knowing they will make another sale in a certain time period.
Cover cost and a few percent, that's that.
And once you control a certain percentage of a market, you don't really bother about loosing customers.
It's rare that a customer changes his price range for a certain good because of a bad experience, and when there are only a few companies in your target range, they will loose as many customers to you as you loose to them.
And once again, the US market is in an obscene state since the early 2000s.
Comparing what you pay for a washer today to even the early 2000s is depressing.
The 6620 retails at 1000$.
That's 650$ in 2000, 200$ in 1975 or 90$ in 1950.
In 2000, the Neptune's where smaller, less featured and less attractive overall.
And they were 1000$ IIRC.
In 1975, 200$ might have gotten you a very BOL TL.
A good washer might have been 400$?
And 90$ in 1950 wouldn't have gotten you an automatic at all I'd guess.
And now consider the 6620 is midrange?
You can get a cheap washer for 300$ with the same internals as a 1000$ TL.
Same stepping as above, that is 200$, 60$ and 30$ respectively.
Not blaming consumers or manufacturers or anyone in that chain, the market is what it is, but you just get what you pay for.
I'd be ready to almost guarantee you that if you spend the equivalent of 300$ in the 50s today (3300$) on a washer alone, you'd probably be still using it in 30 years.