FWIW I've not bought ONE single 'maternity' item of clothing for either of my pregnancies, and I have ended up carrying HUGE out front. I find anything labelled 'maternity' is like anything labelled 'wedding' - automatically costs more just because it's something you buy because you feel you have to, kwim??

I hate buying clothes online as I'm not a 'standard' shape (ie my bust/waist/hip ratio is not the 'normal' ratio, I have big boobs and tiny hips) so I try to avoid that at all costs as I've always been dissatisfied with the fit of clothes from unfamiliar labels (eg I have no problems ordering online from, say, Supre, because I shop instore there a lot and know exactly what size is perfect for me).

You could always just go around to the regular formal outlets in your area and find a dress that falls from the bust (empire-waist, I think they call it?) - a baby-doll sort of style that has plenty of room for an expanding belly, but without the 'maternity' price tag, and you can wear it when you're not pg because it's not cut specifically for a big belly, kwim? I bought my wedding dress from a regular boutique and I still wear it pretty often for special occasions - it was very cheap and cut beautifully to accommodate my growing belly (I was 5 months along when DH and I tied the knot) but still looks great when I'm not carting around a bub