I'd suggest a more accurate comparison would be the total prize fund, not just first. Mind you, I don't have the time or inclination to make a comparison, so this is just one person's opinion.
Many of the US Pro Billiards Events pay high for first, but if you don't finish in the top 3-4, you can't even break even on entry fee and travel costs. [...]
I'm going to push back on both pieces of this narrative a little.
Total prize fund is a good measure if you're comparing events of similar size and can be misleading otherwise. Consider events with $500 entry and $50K added. The prize fund will vary a lot whether it is 64, 128, or 256 players [82K, 114K, and $178K]. But these three events will all have a 1st place prize of around $30K and will be similarly hard to win. They won't look all that different to the top pros.
The distribution (prize fund falloff) doesn't vary all that much. Here I compare the US Pro Billiard Series event (Puerto Rico) that just finished to the International Open from a few weeks ago. Both had 128 players, so it is apples to apples. With my "first place prize" measure, I call the US Pro Billiard Series event $25K, and I call the International Open $30K, i.e., 20% higher. Below are the details.
First, the total prize funds are $100K and $114K. So INO is 14% higher, not 20% higher.
Second you will notice both pay 25% of the field and the payouts are essentially the same for those who finish 5 through 32. So this actually makes the International Open a little more top heavy with 58% of the prize fund to the top 4 (as opposed to 52% for the US Pro Series Event)
When talking about how much money is in pro pool, it is common to compare to a favorite spectator sport or to some other goofy gaff competition. But there is only one reasonable comparison that actually informs pro pool's trajectory, and that is how do we compare to ourselves of a few years ago or a decade ago. By that measure we are exploding. Between men and women, and with the $20K 1st place standard, there are this year 25 events! (13 10-Ball, 9 9-Ball, 1 8-Ball and 1 One Pocket). This would, I believe, be in the single digits anytime before the pandemic going back a long time.