To be fair the people quoting aren't actually printers are they, they are resellers.. That would be why the customer has asked for 170gsm and only one person has quoted for it. (To the other poster - consider scoring your leaflet depending on the content - 170gsm is borderline for cracking).
I should say I don't think you are a printer either Gavin.
Nope, they're buying off a ganger and there's the rub. The margins are very tight and that is to be expected. Every other person thinks they are a printer now, and all those people have got to try make a living. I'm b***ered if I would do a job for £20. With six figures of investment I would rather sell it all and retire rather than be a busy fool. It's all well and good selling at those kind of prices, but what happens when you get a file that doesn't flattern properly, where fonts aren't embedded or worse still it's in Publisher. There's no room to breath at those rates.
The other thing that people miss is that quite often there's a major benefit to running more than one design. WIth all the resellers they can't do this, but for the price quote below (£295 for the spec the OP actually *asked for*), I can run two designs. You have the ability to test then, and that's invaluable.
The printing and graphic trades really depress me now. Any monkey with Photoshop thinks they can design, and whilst the advent of the gang printers has made print more accessible for smaller companies, the fact now that every ganger has 50/100/1000/2000 resellers means that it's a massively saturated market (cue low prices, low margins, bankruptcies etc).
Anyway, 'nuff said - it isn't sustainable and something's got to give. Fortunately I don't work down at those kind of print runs; the smallest runs we do are around £250, and we don't gang jobs together.
Edit: Just to say I misread the post - this is just a DL leaflet, not a DL 6pp. So based on that I could probably do 12 designs for £295