Expensive compared to what?
I resisted getting a Brompton and had three full-size folders before it.
My main objection actually wasn't the price (as at that point, I didn't know how much they were), but more the small wheeled thing.
The first one was bent out of shape when it was run over by a car, so I can't hold that against the bike. However, both of my Dahons cracked the seat tubes. One after 5 years (bought new) and one after 1 year (bought second hand while I tried to get someone to admit responsibility for the first one cracking. I failed).
Both bikes ended up being binned as there were no parts worth salvaging. I only kept the wheels as I'd upgraded them from the cheap vaguely, but not quite, round versions that came with the bike. My original Dahon was about £800, plus the new wheels at about £125 doesn't make it that much cheaper than a Brompton anyway. And the second one I bought from a mate who'd used it for about a week, for £150.
This is a picture of the second one I bought - which was a 2008. The one I bought new, was a 2009. Sure I've got a picture of the cracks somewhere, but not to hand.
When I eventually bit the bullet and got a Brompton, I wished I'd done it years ago.
There's nothing better suited to the purpose that's any less expensive. And actually, There's nothing I've seen that 's more expensive that's any better suited.
My only gripe is that when it's folded, it's not light to carry. And those little wheels do NOT make it easy to wheel about.