Tesla only worked for Edison (i.e., for the Edison Machine Works) for about 6 months. He claimed that he had been offered a bonus of $50,000 (about 40 times his annual salary) for some design work, which he did, and then Edison refused to pay, offering him a 50% salary increase instead. That's the story from his autobiography. Edison's records and Tesla's diaries say nothing about it.

Tesla's salary ($100 per month) when he was working for the Edison Machine Works was the 5th highest in the company, of 39 employees. Only the manager (Charles Batchelor, who had asked for Tesla to be employed) and the superintendent were paid substantially more ($250 and $166 per month respectively). As the highest paid engineer at the Machine Works, Tesla was paid for his contribution, even if not with the bonuses he felt he deserved.

A few years later, he developed his induction motor, which was licensed by Westinghouse. Tesla was paid over $100,000 (about $3 million in today's dollars), plus a generous royalty. Within a few years, Tesla was a millionaire (in 1890 dollars), thanks to the royalties. Whatever Tesla's troubles with Edison had been, Westinghouse didn't betray him or screw him over. 17 years later, Westinghouse was in very serious financial trouble, and couldn't afford Tesla's royalties any more. With Tesla's agreement, the royalties were stopped, and Westinghouse bought the rights to his AC patents for $218,000 (1907 dollars). This might have been a quite poor financial decision by Tesla, but given that otherwise Westinghouse might have gone under. That $218,000 is worth about $6 million in today's dollars, so Tesla was not left poor by the deal.

Tesla proceeded to spend enormous amounts of money on his ideas about wireless communication and wireless transmission of power. This soaked up his own money, and also that of investors (e.g., J. P. Morgan gave him $150,000 for his experiments in return for 51% of his wireless patents that were to come from those experiments). Tesla's lack of success was probably at least partly due to his faulty understanding of the relatively new science of electromagnetic waves - he was convinced that Heinrich Hertz's pioneering experiments were wrong (which implies he also though Maxwell's electromagnetic theory was wrong). Without the break-throughs he expected and had promised, Tesla's money (and that of his investors) was gone. Tesla's financial troubles for the rest of his life were not due to Edison, Morgan, or Westinghouse - they were his own fault.