This may sound like a troll and nitpicking response but.... I would argue that if there were no rule against it, then it would NOT be cheating at all.
I am a fan of thinking outside the box, trying to get ahead the best way you can... and forget about "the spirit of the game". If you're doing something that bad, then it's up to the organizers to not allow it by the rules, otherwise it's not cheating.
The rules require all participants to conduct themselves in a sportsmanlike manner. (I don't have the rule book handy for a cite, but it's near the front.) Annoying your opponent for the purposes of gaining an advantage isn't good sportsmanship, as are many other things mentioned in the rules, specifically. However, any unsportsmanlike conduct used to gain an advantage is cheating.
Now let's relate this to the topic of this thread, which is cash prizes. The existence of that cash prize creates two problems for people who wish to attend tournaments where all of the participants conduct themselves in accord with principles of honor, fair play, and sportsmanship. The most obvious one is that it creates an incentive for people to cheat. People are more likely to cheat for $1,000 than for a trophy. The second one is less obvious. It limits somewhat the TD discretion in enforcing the rules. If I decide that one of my players in my cheap, prizeless, tourneys is not being a good sport and that his conduct reaches the level of cheating, and I penalize him or expel him from the tournament, there's no real harm done. He might be angry with me if he thinks I have acted unfairly, but that's about all. Suppose, on the other hand, that I do the same thing in a tournament with a substantial cash prize. That's a much more serious situation. Money might change hands in substantial quantities based on my decision. As a TD, I'm going to be a lot less likely to act in such a case.
There is a solution to this problem, at least partially. If cash prizes were the exception, rather than the rule, the ordinary tournaments, where people learned, practiced, and set expectations, could be conducted with principles of sportsmanship emphasized above all else. That would set the expectation for all tournaments, and those ideals would be ingrained as part of the culture of the Chess community. Then, at the big tournaments with the cash prizes, the expectation of the community would be that the directors would enforce the same set of standards that they were accustomed to at their own, "less important" tournaments.
At least, that would be my hope. If that is perhaps an overly optimistic view of human nature, I'll stick to it anyway.
Not all. Mine cost ten bucks- three of which goes to charity. My favorite one to attend costs five bucks, and it's a quad with a 16 dollar prize per quad.
If there are no such tournaments in your area.....host one. Finding a site can be difficult, but it isn't impossible. The tournament itself is no big deal.