It depends on the guy, but this sounds like a case of your guy wanting to please his family. "I think we should have a big wedding" usually translates to "My mom always wanted to see me walk down the aisle and my grandmother will be sad if she hears we got married and didn't invite her and also my aunt and cousin who I haven't seen since I was 12 will want to come, etc." If he says he wants to have a wedding, then it's important to him. But this sounds like he thinks its important to do for his family and also in the end maybe he thinks it'll be nice to have family and friends around.
If you had asked me a few years ago if I wanted to have a formal wedding, I probably would've said no. But after going to weddings of friends in recent years, I can see the appeal. Also, I can see why you'd want to elope. Ultimately, you want to both agree on how you'll spend the big day. You don't want to look back with regret.
So since you're at the point of no return, remember that he's probably doing it for his family. Deep down he may agree with you about eloping, but he knows this is the right thing to do for both your families. It might be stressful now, but in the end you'll have fun with your friends and relatives. Planning a wedding is the first real step for a married couple. It's where you start to learn about compromising, picking your battles, etc. It's impossible to please everyone, so just try to do the best you can and remember that this day is for you and your fiance, not just your family.
Everyone has different views of perfection. Mine would have been getting married in jeans and sneakers at a courthouse; his involves a traditional buddhist wedding (the irony being I'm the buddhist, not him) on the other side of the state near our families so everyone can enjoy the day. I think so far I'm the only one not enjoying the stress of planning it all, but I'd rather him be happy with something that's important to him. If I need to stress out a bit and dress up in something I would never otherwise consider, I see it as a small price to pay to give the love of my life something he truly wants.
Perhaps he's worried you might regret it down the road. It seems that a lot of people who elope end up wishing they'd had a more formal affair later in life.
"Oh, I wish we'd had a picture with my grandma at our wedding... she died that summer."
Stuff like that. And, let's be honest, half of the reason you're having the damn wedding is for your families, and decidedly NOT for you. Everyone feels the need to throw their opinion out during the planning phase... it's rather stressful. Ultimately, it sounds like it's too late to go back on what's in motion, so just let it ride. You're going to have a beautiful day with the man you love and, what's more, he cares so much about this day that he wants it to leave a lasting memory. So many guys are just along for the ride... take pleasure in knowing you picked someone with a big heart.
If he wanted the big wedding, he should be planning the big wedding.
Simple as.
I wanted a wedding just big enough to make my wife happy. That is all. I would've been OK with eloping and doing it someplace else entirely and saving a mint and a lot of time and effort.
I think that in retrospect, if she could do it over again knowing what she knows now, she'd probably opt for eloping too.