I've just bought one and yes they really are expensive but worth it in my opinion as they are so easy to clean, in addition, redmite have nowhere to hide in them, that was one of the reasons for me purchasing it in the first place. Worth paying that bit more for your birds comfort really.
They are very well designed, sturdy and easy to move around the garden, I must admit to being happy with my purchase. I believe it will last for many years as its not just flimsy plastic.
Just after I bought it however, a friend pointed me in the direction of a company called "Solway Recycling" (find them on Google). They also make a plastic henhouse from recycled agricultural plastic and it looks the business,(they also make pig arks etc from plastic as well) the run is smaller than the Eglu but it's about 100 quid cheaper, it also holds I think 8 birds, so that may prove more popular than the Omlet product. Had I seen it first I would likely have bought it before the Eglu, but as I mentioned, I'm very happy with what I bought and my chickens seem very chuffed with it.
Anyway, I hope this is of use to you.