CynthiaF I've won almost every expedition where I was trying (there have been a couple that I sat out because I was busy with RL) and I've never spent a dime on them. It's entirely possible to win expeditions without spending cash if you can spend time. I'm retired so I can check every hour or so to collect production, send ships for materials, finish jobs and start the next round of production.
I don't see how you can know that the winner spent cash unless they did something like finish the first day (& not on the Winter Event expeditions where they could gather bucks for the 2nd & 3rd expeditions before they started).
I finished the current expedition 1st on Monday afternoon. No dynamite was used. 2nd place is about half way through phase 2. 3rd place finished phase 1 and has been sitting with that score for a couple of days, 4th place is moving up slowly. Of course, there may be a quiet accumulator of bucks ready to pass them.
The only thing I've spent money on is event passes a couple of times and I think I bought a ship early on.