Warning! Long and rambling due to lack of sleep....
I bought my dress about 15 years ago - I was engaged then and even though I didn't have a date set for the wedding I thought I'd look at dresses. I went into one store that had a mega sale, found a dress I liked that was affordable ($298) and bought it. I also bought 2 veils because I couldn't decide which one I liked better, I think they were $50 total for both. Ended up breaking off the relationship later that year, but kept the dress and veils.
Now since I have the dress already, and I still like the dress, I'm planning on wearing it at my wedding next year. After all, I bought the dress for my wedding, it's just later than I thought it would be.
Having said that, if I didn't already have the dress frankly I think I'd just rent one. Now maybe this is from the fact that I'll be 35 when I get married, or possibly because I've spent the last year or so slowly sorting through my clothes and giving bags away to charity. But realistically speaking I'm never going to wear my wedding dress again, so it's total useful life will be about 12 hours. Unless it's in style years from now my daughter (should I have one) likely won't want to wear it. It's going to sit in a box, be looked at occasionally and then eventually either sold or thrown out. Sad but true.
When I was 20 all I could think about was the dress. It was THE most important element at the time. And the church had to just be right, and I must have looked at 20 reception options. And expensive invitations, and wedding favours etc etc.
Nope, if I didn't already have a dress there's no way I'd be spending the money to buy one now. I'm not buying a new purse, I'm not buying expensive & uncomfortable shoes, I'm not spending a fortune on undergarments. For me now it doesn't really matter what I'm wearing when I get married. It's not the dress that's important, it's the marriage.
I'm not even picking out what my Maid of Honour will wear, or suggesting any colours. I don't care about colours. I have 1 MoH (no other bridesmaids) and I'll be happy if she shows up in a nice pant suit. All total the wedding & reception will last under 12 hours. It's a lot of money to spend for 12 hours.
BTW, FWIW my entire budget is under $25K Canadian. That includes return airfare & hotel in Vegas, the wedding, photography, reception and all related trappings, a week in Anaheim right after (for DL and to touch base with family there) including hotel & park passes etc, and then after a short break return airfare to MCO for the honeymoon, 4 day
DCL cruise, a week at WDW (hotel and park passes), Discovery Cove, car rental, tips, and meals for 2 throughout the entire thing. That also includes the invitations and any needed alterations on the dress. If for whatever reason I can't wear the dress, then the alterations $$ should cover a dress rental.
I'm still still trying to come to grips with spending $25K for 2.5 weeks.