At the end of the day you get what you pay for, the photos Chinese websites use are stolen from the original designers, and if it arrives and its horrible you have no fall back, its very hard to communicate with them and you rarely get your money back. if your looking for a cheaper alternative try etsy, you can see how many "stars" each store has. A friend of mine got a dress for 200 euro from it and she loved it. You could also try Dresses 4 Heaven in Dublin. They apparently can replicate most dresses for cheap, and you at least get fittings on site and communicate with real people, they have quite an online presence so you can see real feedback.
It was only when I went dress shopping that I realised why dresses were so expensive, they work that goes into the structure of some of them are amazing, my whole bodice is boned so I wont even have to wear a bra with it and there are extra bits that hold you in, in all the right places. You wont get any of the real structural work that goes into wedding dress with a cheaper version but if your not bothered by that then defo try Dresses 4 Heaven! Good Luck