Why should we be surprised that the company whose business is in shipping and selling a wide range of physical products has more revenue than a range of companies whose income are either service fees or advertisements? We're not comparing like with like; Amazon's revenue is counted against by buying and stocking the physical products they sell to derive that revenue. None of the others on that chart have physical product to worry about and so retain a much higher percentage of revenue for themselves.
I think saving money on designers can be justified, after all ;-)