Cheaper power supplies and electrical stuff means higher likelihood of failure (often frying other components in the process), cheaper capacitors mean higher chances of leakage or blowing, spinning HDD instead of an SSD means higher chance of drive failure, cheaper plastic means a case more prone to becoming brittle with age and cracking, etc.
- premium laptops have more fragile and less optimally placed hinges though
- thin lapops have ultra thin internal connecting cables and commectors, which are really unreliable compared to other solutions that won't require tweezers to handle them.
- everything thinner and more silent means more heat and worse cooling
- keyboard lifetime cam suffer too from too shallow builds
- it's been a while and it didn't happen often (i think twice if i'm not mistaken), but when my chunky plastic laptops fell from a table, nothing happened, while i've seen enough pictures of dropped Macbooks made of metal with at least bent casings, if not worse damage.
- do they still put spinning drives into systems? and if so, "expensive ones" had those too not too long ago (relatively speaking, as i'm an old fart)
- capacitors that were prone to fail (after several decades of use!) were a thing of the 80's or 90's mostly.
funnily my old systems still are working fine regardless, though i admit it is not good practice that i haven't replaced the capacitors in those yet.
i don't have data to back up, but i've personally not really heard of anybody in real life who had big trouble with their systems failing.
while funnily i've often read of people claiming their superior lifetime Macbooks, who simply had to replace their keyboards, their screens, their logic boards just once or twice and still are happy how reliable these are.
note that i don't think that this is because Apple is building "non-lasting systems on purpose" as i'm sure ultra thin premium laptops from Dell, etc. will face the same, or similar problems.
thinness comes at a cost.
though i know somene in real life who has fried two of his iMacs over the years