This issue is mostly related with the changes planned in #79
The company's growth will be retarded when the maximum salary is set to a certain maximum level - since there's no obvious to invest it anymore. That'd make a bad experience to players also, since they can't improve themselves nor their companies.
Because of this issue it has been discussed to set a maximum limit of players that a company can bear (maximum limit should be no higher than 30)
Also note the maximum limit at the beginning should be 5 or a few more.
How this thing is related with investment is that you can increase the limit by investing more. The amount that should invest in order to achieve more limit should be exponential, so players can spend their money earned by high paying salaries on them.
For example, the maximum limit and the amount invested should have a relationship like below

So players have to buy new companies as it is hard to buy more space for their workers. This would add more challenge to the game as well