OK, I see why you are saying that each player really only has $5000 of bankroll to bet with, but your logic is faulty. Think of the team as one single entity, not as five players.

(As you stated, assuming that each player has equal skill and is playing equally good games may be an oversimplification - but it is a good approximation, assuming that everyone is playing a mathematically sound system and knows about pen, rules, spread, and all that.)

Therefore, you have one entity playing at a given game with a given spread to a bank of $25,000, NOT $5,000. Clearly, given the same risk, the base betting unit must increase.

If you got 4 people to give you $5000 each and you were the only one playing, the effect would be the same. However, with five people playing, the time required to play X number of hands is cut by %80.

Hope that helps.

Blitzkrieg