The regs usually prohibit experimental aircraft carrying passengers or freight for hire. So you can't be an airline or charter company.
But I don't think it prohibits you earning a fee or a pilot flying it for a fee.

Let's say you homebuild a new design acro plane, and it is a real whizbang worldbeater. You hire Patty Wagstaff to fly in it airshows, and the appearance fee might be $12,000 , split half between the pilot and half the builder.

Same for the Reno racers, many of which are experimental and some even amateur built. The top unlimiteds are often flown by some expert pilot, not necessarily the owner and may win hundreds of thousands of dollars.
An example of this was Rick Brickert flying the homebuilt experimental Pond Racer, which did not win anything, but would not have been illegal if they did. There was no passenger or freight being carried.

Some pilots may be flying for the challenge and fun of it, but many may be earning a fee also.