From the conclusion of the paper:
"We found that marriage duration is either not associated or inversely asso- ciated with spending on the engagement ring and wedding ceremony. Overall, our findings pro- vide little evidence to support the validity of the wedding industry’s message connecting expen- sive weddings with positive marital outcomes."
So...either spending more either has no impact or a negative impact on how long a marriage will last. Well.
I suppose that if one began with the belief that spending more would effectively buy one a better marriage and is therefore gobsmacked to discover that money can't buy love, as it were then this would be a bolt from the blue. Otherwise it's kind of a nothing concussion.
But beyond that, the whole premise is shaky.
What is "a lot" to some earners is a rounding error to others; would have been a more interesting paper if they'd measured what was spent as a proportion of overall assets rather than spending per se.