The thing that gives a cheap pair away is never obvious in the shop. It's three months in, when you sit down at a desk or in a car for the fourth time that week and the crease at the front has gone soft and wandering, no longer a line so much as a suggestion. A proper pair holds that crease, or at least knows how to take a press again without the fabric going shiny on you. That's the detail nobody mentions when you're stood in front of a mirror admiring the cut.
What separates a good pair from a disappointing one comes down to the cloth and the tailoring around the waist and seat, which is where blazer trousers either sit well or sulk. Wool or a wool blend with a bit of structure will keep its shape through a working week and a train journey folded into a bag; pure polyester with no give in it tends to bag at the knee by the second wear and never quite recover. Check the waistband is faced properly rather than just folded over and stitched, and that the fly has a proper hook and bar rather than a single flimsy button doing all the work. Lining matters more than people expect, a half lined pair will crease in places a fully lined one simply won't. I bought an unlined pair a few winters back thinking I was being sensible about cost, and by autumn they'd gone through at the inner thigh from nothing more dramatic than walking normally.
Where they come unstuck is pairing them with anything that's trying just as hard. A soft tailored trouser wants an easy top, not another structured piece fighting for attention, so skip the stiff blazer on top unless you enjoy looking like you're heading into a meeting about nothing. They also don't love chunky trainers, which drag the whole look down into fancy dress. As for colour, navy and a proper charcoal are the ones that behave themselves for years, taking you from most situations without complaint. Black is fine but shows wear at the knee and seat faster than you'd think, and pale grey, lovely as it looks on the rail, marks if you so much as look at a coffee cup.
They're the wrong choice if you want something to live in at the weekend, because the tailoring that makes them look sharp is exactly what makes them feel like clothes rather than comfort. For a desk day they're unbeatable. Tomorrow I'd wear mine with a plain fine knit jumper and loafers, nothing shouting, and let the trousers do what they're good at.