Bad assumptions lead to false conclusions. The bill was originally $30. It was reduced to $25 and $3 dollars were returned to the men in the room....$28. Each man had then paid $28/3 or $9.3333333. Not $9. 28+2=30.
Ahh... but the roller is not welded.
To assume that the roller tip acts as if it was welded is wrong. The roller transmits the force in a line parallel to the valve stem from the center of the roller.
I should add that this is assuming that whoever did the valve job got the tip perpendicular to the valve stem. Otherwise the force from the roller center will be applied perpendicular to the valve tip angle and generate side forces on the valve stem.
There will still be doubters and all things will still add up to $1 missing.