Using The East Coast Steel Challenge Championship match as an example. Ontelaunee Rod and Gun Club (a private club in Lehigh County PA) is the facility that hosts the match. It is not run by the club although some club members are very involved in running and organizing the event. The group that runs the match pays the club for use of the facility. Between set up, match day's and teardown, a week or more is needed. There are utilities, insurance, grounds keepers, upkeep, infrastructure and repair to name a few expenses. Try to imagine what it takes in facilities to have 4 or 5 hundred (or more) people show up at an event, you need a lot of support, parking and so forth to accommodate this large of a crowd.
About 3 years ago Ontelaunee constructed 6 new competition only pistol ranges to add to the 4 they already had, this allow them to run large matches without causing a big disruption to normal club activities. The cost and effort to construct the new ranges was considerable. In the case of Ontelaunee the club made the decision to construct the ranges based on the premise that it was an investment that would have a gradual payback because they had been running level 2 & 3 matches for years but had to close down the club for the week which of course put the club out of bounds to the regular membership on a regular basis. They constructed a parking lot that is actually bigger than most club ranges in the area. In a geographical location (Eastern PA) where there are gun clubs everywhere, there are actually few clubs that have the facilities to run big matches.
Local/monthly matches are generally staffed by shooters themselves. Level 2&3 matches have (for example) dedicated ROs. Some of them are, depending on the situation, given travel and room/board compensation and/or discounts on their match entry fees. As an example, I'm local for the East Coast Steel Challenge but will RO five of the seven sessions. I get $25.00 per session. So in effect I will shoot 2 guns for an approx. out of pocket $25.00 total, this particular match draws over 500 shooters from all over the country, many of the top shooters and pro's attend it. I don't need a hotel room but do get food, it's still a LONG weekend and I will take 2 day's off from work. If I wanted to I could apply to staff the National or World Speed Shoot (Steel Challenge) if accepted I would have some of my expenses paid out of match entry fees.
Big matches do get sponsors to donate prizes but many will augment the prize table. Also there will be cash prizes for class winners/placers and some have Lewis Class payouts. A good prize table will attract more shooters. Last Year at the ECSCC, between the shooters prize table and the staff table I came home with about $500.00 worth of stuff and didn't have to pay to shoot the match. But I did put in a lot of time/labor. This is not a comprehensive summary of match costs and expenses but at least a partial explanation of why the big matches have high entry fees. As I mentioned in a post upthread I didn't enter the Mid-Atlantic Sectional because I'm shooting plenty of matches this year, In USPSA I haven't shoot many matches in the past few years. None of us can do everything but I'm shooting in 2018 at least five level 2/3 matches and a ton of local matches. Next year will prolly shoot this sectional.