In my perception the line is not so much a cheap/less cheap distinction than going roughly perpendicular to the novelty axis, separating fashionable from timeless. It's as if product management would intuitively combine short-lived aesthetics with short-lived materials. Maybe they know from the beginning which new releases are merely novelty and which are intended to become permanent fixtures in the programme?

It would make sense on many business levels (e.g. I'd image negative impact of flimsyness growing almost exponentially with each year a bad product stays in the catalogue, designing for cheap or sturdy being muchbless costly than designing for cheap and sturdy and so on), but I have no idea if Ikea are good enough to consider that consciously (I do think they'd at least be closer top that level than most others)