There are probably several local maxima on the distribution curve. At some point having dogmatic, extreme ethics probably hampers getting everything down, and the worst, most cartoonishly evil company also is leaving money on the table. In the less extreme, I think you probably have three schelling points. 1) High-Integrity companies that promote and use the culture of ethics to attract customers and employees. It probably is industry specific if this works. 2) You have "ethics agnostic", but legal" companies that just do focus on near-term profit maximizations and while they may have individuals trying to make ethical choices, the organizational structure won't reward that outside of the whatever profit it generates. Non ethical behavior that gets bad press or crosses idealogical lines, gets dropped fast if not profitable and arbitrarily depending on leadership otherwise. 3) Then you have companies covering up illegal/fraudulent issues, where the incentives are to double-down and reinforce the behavior.
Depends the environment you're working in - there are several cultures within the US where I think your statement is quite true... but in general people find that working for a company that doesn't care for them is a detriment and will demand higher compensation due to the obvious risk. That all said - you should always be defensive as an employee about how much risk you accept on yourself since the employer/employee relationship can be terminated suddenly and without any real recourse in most circumstances.
Depends on the circumstances. If you are trying to make a valuable product, good ethics will probably serve you better than bad ones in a majority of cases. If you aren't concerned with generating real value and are fine with running your company and reputation into the ground, then sure.