Okay, let's try costs.
PA: They say a 255 page book is typical. A $19.95 cover price is typical. The highest discount in the contract is 30%. Copyright is $30.00.
Total cost to the author for 500 is: $6,982.50 + $30 = $7,012.50 out of pocket for a PA author, ignoring shipping and handling.
If the author goes to a local short-run printer with the same 255 page book, for a 6x9 softcover, perfect bound, four-color cover, he's looking at $5.75 per book, or $ 2,875.00 for printing. Copyright is still $30. ISBN is $225 for ten. (Note: In the quantities PA is buying them, the cost per ISBN is far lower.)
Total cost: $3,130.
If the author goes to iUniverse:
Basic package is $459.00. For 500 copies, the author discount is 55%. Typical iUniverse price for 255 page book is $14.95. $3,363.75 + $459.00 = $3,822.75
Author sets selling price for own book at $15.75 (average price for a trade paperback in the USA). For iU and PA, use the list price. All 500 sell:
If the author sells 'em all:
PA: $9,975 - $7,012.50 = $2,962.50 profit, not counting shipping&handling.
iU: $7,475 - $3,822.75 = $3,652.25 profit, not counting shipping&handling.
Self: $7,875 - $3,130 = $4,745.00 profit, not counting shipping&handling.