Louis Pesteur costs about the same as three other mad scientists (Kyle, Willian, and Jen), and in order to keep up with them and invent as many gadgets per turn, he needs even more money. And he doesn't give you a discount for inventing.
Here's the thing: with my standard starting posse (Jake, Irving, William, Kyle, Jen) I have enough money and I invent gadgets for cheap, so I can play cards like Faster on the Draw and This'll Hurt in the Morning, that help me defend against early aggression, and go on the offensive when I'm ready.
Louis Pasteur wants more money. If I start him I lose William's discount, and I need to pay extra to invent several gadgets per turn. I need additional income. I want to be playing One Good Turn and Reserves. This will leave me more vulnerable to early aggression.
It's tricky to balance the deck to support both a five-dude start and an anti-clowns Pasteur start...
P.S. and yes, shuffling several low-value dudes into the deck will make me fail pulls more often. While not a big problem if I'm using Louis' unbooting ability, failing to invent a gadget and having to discard it would suck.