The biggest costs will be food, venue, and usually photographer. I found a really good reviewed freelance photographer and booked her for 3 hours and it was $450. I personally find that was a great way to cut cost, and her portfolio looked good enough for my taste (way better than anyone I know personally, but not magazine quality).

Could you slim your guest list at all? That helps limit food and venue cost a lot of the time. More guests means you need more space and (obviously) more food. Do you want alcohol, too? Food + drinks for 75 people will get pricey. I'm not sure how you feel about it, but you could always make it sort of a pot luck.... to some that would be a mortal sin, but if you're already well established and not asking for pricey wedding gifts or for people to travel a long way it wouldn't be tacky (in my opinion). And I'm sure many families may be excited to show off their signature dishes.

Another way to cut cost with the dress is to purchase a white bridesmaids dress (or blush, champagne, whatever). Also, Modcloth has beautiful white "Bridal" dresses that are more affordable than preowned (in my experience).

I hope this was a little helpful, and not totally TOO untraditional advice! Good luck! My wedding is on a budget of $8k, but we only invited 40 people for reference.