The average wedding in NYC is EIGHTY THOUSAND DOLLARS. Sure, most weddings do not hit that number, but many weddings are at least 5K to 7K. That is a lot of money, especially when it could be used for a down payment on a house or a car to get back and forth to work.
I think you can convince him to have a wedding if you do it on a strict budget.
When our dad passed away, my sister had the "Celebration of Life" event at her home, which was a cocktail party atmosphere with substantial appetizers served. She rented all of the glasses and appetizer plates and utensils. She bought napkins at the dollar store. She bought platters of food from restaurants. She bought 'bake in the oven' appetizers from Costco's freezer section and bought various dipping sauces. She bought the booze. She hired a neighborhood teenager to put things in the oven and take them out. She hired a bartender.
We had 85 guests and the total cost was $1,500 for a six hour party in her back yard. The only extra cost was a quart of paint for her front door and she needed to replace some old lawn furniture. She borrowed some tables and chairs from a neighbor.
In the middle of the party, my engaged niece saw how lovely this party was and decided to duplicate it for her wedding day. She took the ten grand she saved on what she would have spent on a wedding reception and bought a better house. Imagine that, a $1,500 reception. You see, you take the word wedding out of a party and you save ten grand. Honestly.