We have collaborated with a lot of other races in the past to help save costs. Usually that just means another crit and we'll turn it into an omnium with overall winners. For the Chicago Cross Cup we have trailers that have almost everything you need to put on a cross race complete with stakes, snow fence, generators, heaters, tents, etc.... but it's been assembled over the last 12-15 years and we as a series charge every promoter who uses it by the rider count in addition to the usac fees, etc and as a part of that series a ton of people get comp'd /free entries.... like SRAM who we specifically never get any direct benefit from.
As a part of the ICA (local USA Cycling Association) we have a race promoter trailer that has some community purchased materials. A stage that is modular. Lots of cones and signage "race ahead". Vests for volunteers, rudimentary podium. Then as a group we had a registration and race day "software app" written a long time ago that works with the USAC rider database and our chosen reg platform (BikeReg) and controls everything day of. It allows all of us to use the same system so we all get fast with it. If you've ever done races here and then gone to do a race in Wisconsin you can see the immediate difference. You can be in and out of reg in a minute or two here....not so there.
We pooled resources and have computers we own that run the reg system, printers, ink/toner, a finish lynx camera system for results, etc. We pool and collaborate a lot.
I was race director for a duathlon once. I was talked into it. I had to contract with a timing company for it. Only like 2 timing locations and disposable race number based chips. I think I paid like $2k-$3k just for timing services. At one point I was looking into buying a setup to use for our races and then do running races with it on other days just to help pay for it.
Having my omnium setup allowed me to cut the $500 for straw bales in half which ended up making one of the races break even.