Traditional labor theory can make arguments for both, if you put in most of the work, then you deserve most of the benefits. However the case for equal pay is also solid, especially if the fruits of labor are abundant. How much does 5 million give you that 1 million doesn’t, and why shouldn’t you settle for 1 million if it means everyone would get more?
But from a leftist perspective there is a fault in the question (but it is still a good question). Namely that you sell the business. In an ideal left world, you wouldn’t do that. The business belongs to the workers. If the workers can all form a consensus that it is time to leave the business and sell it to another set of workers—those that leave will be bought out basically—then this is a valid scenario. However if under a new leadership, some workers are receiving more benefits then others, then that is exploitation. I would say actually that the new leadership is exploiting their previous workforce by spending the money the workers created by buying a new business without their consent.
So in short, you as the founder of the business that was bought, are enabling exploitation by selling it to a larger organization (unless you sell it to a worker owned and operated business).