I don't want to think Plank took the money. I don't want to think that the money is missing. I want the best for everyone, the attendees, the prize winners, and Plank, but I'm having a lot of trouble believing this event cost over $20,000 to host.
I don't think he had quite that amount of revenue.
Assuming there were no overlapping player: 151 Brawl + 243 Melee =394 (call it $400)
Assuming every single person entered Singles and Doubles = 400 X $50 ($20,000 for Singles/Doubles/Venue)
$20,000 is therefore your MAX that Plank took in. I'm ignoring spectators for the moment.
Lets subtract what we know:
Only 96 players entered Brawl doubles, which is 55 players less than max and $825 off the max
Only 156 players entered Melee doubles, which is 87 players less than max and $1,305 off the max
Now regarding spectators: I think the difference between spectators and people who entered Brawl/Melee more or less offset. Even if they didn't, anything here is mostly guesswork unless you want to dig through the names on each list and cross-compare.
Subtract out the 6 extra people I gave the total earlier: $300
So, Planks revenue is actually
$17,480 AT MAX. This is the highest end reasonable estimate for what Plank took in.
He also did scaling if I recall. I don't know the numbers but using Cache's or trying to recall how many were signed up each month could let you figure out how the numbers work here. He definatelly took in less than the max I underlined above, but who know by how much. If 100 people signed up at the second-to-last chance to sign up, where they would only save $2.50, then that is $250. Now IIRC, the earliest you signed up could have saved you $10, which means if 100 people signed up then that is a subtraction of $1,000. My point is the number add up quickly.
Finally, who knows how many got free entry. If 10 people then that is $500 to subtract from the $17,480.
Anyways, I'd estimate the revenue for Pound 5 was closer to $17,000 (or even $16,500) than to $20,000. Using the numbers that most reasonably represent his max though without any of the guessing is:
$17,480