The phrase "he who pays the piper calls the tune" implies that whoever is funding a project or endeavor has the power to make decisions and set the direction. Synonyms to this phrase include "money talks", "whoever foots the bill has the final say", and "the hand that feeds controls". These phrases essentially mean that financial power comes with authority and control. Another similar phrase is "pulling the strings", which suggests the ability to manipulate or control a situation. In any case, these phrases emphasize the importance of financial investment and the influence it can have on decision-making.