It depends, although the best answer is probably “something less than what you have.” Anyone who thinks you ought to go into debt when throwing a wedding ought to have their head examined.
I have 40 cousins just on my dad’s side, and most were married with kids when I got married, so our choice was to have about 50 present (immediate family, no aunts, uncles, or cousins except for godparents) or to invite about 400-500… you’re starting your family, so your guests expect to bring theirs. The custom in our parts is to provide a picnic-style dinner… not too elaborate, but satisfying enough for the teenagers and manual laborers in attendance. To scale back to coffee, punch, and cake when you don’t have to (again, in our circle) is kind of like saying you aren’t interested in having the family stay around for a good long time to catch up. (Weddings and funerals, that’s when we all see each other!) The food and all that isn’t to impress anyone, but just to give them a good excuse to stay and visit and a good way to make sure their kids are not miserable. In our family, beer and wine, yes, hard liquor, no… celebration without intoxication is the goal. Still, with a nice big Catholic family… not cheap. The same with the decorations and your “costuming”. It doesn’t have to look like a coronation, but it should look like a celebration, within the realities of your standard of living.
What that costs depends on where you live and how much self-restraint you have. If you are bargain-minded (flowers that are in season, less expensive food choices, restraint in the size of the wedding party, family-provided labor), it will be a lot less than if you’re playing out some fantasy of being royalty for a day.
Do some shopping around and ask advice of your local family and friends (if any have gone before). Most will have some if-I-knew-then-what-I-know-now pointers that will be helpful. Then pencil it out, add at least 10% to your estimate, and start deciding what is and isn’t realistic for you.
Mine: Look in some older wedding albums. I think that the most expensive, trendiest stuff is what looks the silliest a decade or two down the road… and you’ll also get a grip on how much of the day should be dedicated to being posed for pictures of yourselves. Beyond the first several of you and your spouse on your first day as such, those pictures of Aunt May and Uncle Harry chatting with your parents will be the pictures you’ll treasure.