It doesn't really work here because what you're trying to describe is a dream vs. a sacrifice type situation, and you've set this up with conjuctive phrase: "Even though".
Even though X, the _________ is Y.
The blank space is where you've put "crux of the matter", but the crux of the matter really means the absolute, fundamental point that underpins an issue. The price of a wedding is one negative factor of wedding planning (the matter), but it is not the "crux" and it is used here out of context.
Even though such extravagant weddings may sound like a dream-come-true, the fundamental issue is that you’ll be wasting a lot of your money.
This is an edited version where I have added "fundamental issue" because it hints at the negative. "Crux of the matter" does not hint at or imply anything negative, and the situation you are trying to portray is a positive vs. negative trade-off.
I would also remove the unecessary "to you" after "dream-come-true" because you say "you'll" shortly afterwards and it isn't really needed.