Give you and idea from what a former student of mine showed me about a year ago after she hosted one of her larger events in NE Indiana. (They own their own octagon but it did cost them $7,500 to have it built).
Venue Rental - $2,500 (Major night club)
Marketing - $3,000 (included radio hosting shows, repeat ads, flyers and online website promotions)
Pro Fights - two scheduled $2,900 included travel fees to all four fighters ($250 to losers $500 to winners)
Insurance for single night event $1,500
Total cost overall was $9,900
Ticket sales were $9,500
Sponsor income was $6,500
Total profit was $6,900
Keep in mind that her and her partner host events all over the place in Indiana and this was one of thier most expensive ones to date. They had 12 amatuer fights and the two pro fights.
She said her average profit is around $1,900 on smaller venues such as fairgrounds and stuff but it always depends on sponsors and this year she has not been getting big sponsor checks so it has been hard on her and her partner. They only hosted three events this year because they could not secure the sponsor money to offset the cost.