This idea is part of a group of ideas related to weddings I had back when I got married and the following years. Not sure if they are at all relevant in 2022, but I hope it can help you find new ones.
After reading Crowdsourcing by Jeff Howe, in a year we had a lot of weddings to attend, I was wondering why nobody tried to crowdsource this information. This is similar to the previous idea and could probably be mixed with it. However, the main difference is that you let your user enter the data similar to what Glassdoor does with salaries or yelp for restaurants.
For the site it could use google map (or another map api) to show potential venues, places, contacts, stores, etc. Once a place is selected, the user can see the rating, the comment and the price other users have entered. They could also enter their price, rating and comment anonymously. Rating and comment could probably be public though to prevent haters. It could use facebook connect or something like that for login and having a verification mechanism like twitter & facebook. This could help to track that the user is real and give valid info.
How to entice users to participate and give valid information?
It could probably be gamified and have rewards like google guide. Users could have points, entering data and valid prices give more points, moderators could rise from those who have more points and are active in the community. Points could give privileges and could be redeemed.
How does that kind of site/app make money?
Well the easy one would be with ads. Real stores could pay to have their name on the site, but that could corrupt the whole idea though. Couples who need help could pay a small fee to have users do tasks for them, find the three best venues for a wedding of 200 people in this price range and book a meeting with each of them to visit.