Have you looked for discount? Have you looked into samples of that dress (meaning it's only been tried on in the store)? They could lower your price like 50% all the way up to 90%. I loooove sales if you haven't read that before. I just dont' see the point in paying a ton when I don't have to. In my case I found someone who can make mine perfectly (and I trust that she can), but there's a ton of stores I found online:
1) Bridal Sample Store
http://www.bridalsamplestore.com/-strse-Bridal-Gowns-cln-Pronovias/Categories.bok for instance they have pronovias at $325 instead of $2000. LOOOVE samples. The money you save, you can get it fitted perfectly at your tailers and kim.
ex just looked and this sample is over 50 percent off it's $650 instead of $1275
This Priscilla of boston is $725 instead of $4250
Pronovias at $425 instead of $2900
2)
http://www.preownedweddingdresses.com/
Uhm here's a secret...they're not all pre owned. You can click the search and highlight you only want "new" or "sample" that will give you designers who are creating their own product, at huge discount, and samples (you can even search for your name designer to see if they have a sample available)
Just putting in a search for a new/or sample dress under $600 (to please your fiance) I pulled up over 1,000 dresses
examples:
custom made dress:
at $599
Name brands like:
galina sold at $300 from $800
Maggie sottero @ $350 vs $950
Keep in mind I don't know your style. I'm just pulling random dresses as examples.
Also you might find your exact style at one of these sites (or find something you love more that's worth more, but you can pay less for...sometimes due to overstock, sometimes samples, and sometimes custom creations...but all never worn in a wedding, etc).