I know weddings costing more than $67.50 are generally frowned upon here. But we had a somewhat expensive wedding, and as far as these things go I think it was more or less worth it. We didn't do it to "show off" or anything. We did it because we had guests that traveled thousands of miles at great expense, so we wanted to have a nice party that everyone could enjoy. Some might argue that doesn't have to cost, but to some degree you have to spend money to make sure everyone has a good time. We did, and people still tell us it was a great wedding. I don't think anything was particularly extravagant, but it still cost $15-20K as far as I can remember. Even with that cost my wife still did the invitations herself, her friends did much of the decorations, I made several pieces for decorations (ask me about how to make "distressed" wood..), we bought the booze and it was held in a pavilion with a bare concrete floor. These things costs unless you go really bare-bones.
The catering firm owned the site so had to use them, and it was around $100/person. For 100 people.. But remember that covers making and storing food, tables, chairs, silverware, napkins, servers, bartender, cocktail hour food and serving, cleanup, prepping the site, ceremony chairs etc,etc,etc. All this you'd have to find or rent on your own.
-Just a DJ was $700 or so I think. That was the going rate for simple ones. Otherwise you're renting speakers and coaxing someone into MCing the thing (probably a friend you'd rather be having a good time).
- Atheist officiant: $300 maybe?
- DIY Booze; over $1,000. People drink a lot of wine.. (We had nothing fancy at all! $9 vodka is good enough..)
- Bus to get people from hotel to/from site? $500 I think.
- I'd say our only splurge was the photographer, because we both take pictures very seriously, and just thought the $1500-2000 looked like garbage (poor compositions, terrible processing etc). Probably almost $5k there including album etc.
Was any of this "necessary"? Not really, nothing in a wedding is necessary beyond signing the paper. But it all made it come together and people enjoyed it and we still remember it. Can you do it for $5? Yeah probably, but I think it'd be hard. But I've been to one that maybe cost that and it was nice, if a little disorganized. I've also been to (probably) $50k weddings that were lame.
edit, to the guy above: An 80 person wedding isn't particularly large. We got nagged by the catering firm constantly for only having 90-100. Most are 150 people and I've been to ~300 person ones. Yes those were crazy, but with two families of aunts, uncles, cousins etc and two sets of friends, many with spouses of their own you get to 80 pretty quickly. And if you invite some friends, you kinda have to go all the way. Or where to you draw the line? More people means there is a higher chance everyone there know somebody and have someone to talk to.
There is also the social contract that I have gone to the weddings of many friends and eat and drink for free, so I should really invite them to mine. Being the host is work. First of our friends to get married said this at his wedding "now you guys get married so I can drink and party"