A quibble, mainly, because I agree with your principle: this would be enough for 1 difference maker, more or less. Money spent on 2 and 3 year contracts make this $51M sum something like $10+M a year. Nolasco territory. A 3 year contract for $51M might have gotten us someONE who would move the needle (although needle-movers generally demand and get more security than 3 years).
Except of course that he'd need TJ surgery in May of his first year.
We shouldn't ignore historical context. The team basically was short about 8 needle-movers and had about eleventeen holes to fill. Had Ryan ignored the Josh Willinghams and instead opted for some $51M "difference-maker", that guy would have been high-fiving about eleventeen empty uniforms after every loss and the needle would have moved even further in the wrong direction.