Why do you say that? I'd imagine they'd throw a party and slash paychecks in half if they could.

It's far easier to fire people and them employ somebody willing to work for half the price. The end result is pretty much identical, but the distinction is in the fact that firms will always prefer to fire people (provided they have good hiring prospects) than slashing their wages, because the price of labour is incredibly sticky. It also depends on the nature of the business two. If the success of the business relies on good infrastructure and human capital, I can't see the desire to slash wages being their in the first place, provided the employees are earning above minimum wage.

No, I'm just assuming that you're not going to pay people who are higher up the same as someone who is lower than them.

There's a threshold where, if the minimum wage is raised, other wages will have to be raised in proportion so they are about as much above minimum wage as they were before. It depends on the size of the company though; for large companies, you'd have a lot of employees who were above the threshold and wouldn't be affected by a minimum wage rise, so not everybody's pay packet would need to increase.