Not sure if my price increases year after year, but for 4 years I would just end up paying $45*4 = $180. I guess Squaretrade replaces Applecare though? Applecare for 15" MBP off eBay is $135, so I guess I would end up paying about the same if I got both Applecare and Statefarm: total = $315.
I rather go with Applecare + Statefarm since I trust both of them more, and together I think its total better protection package since Applecare service can be done at the Apple store.
EDIT: I just looked at it, Squaretrade 3 year warranty is $199.99 and then if you add accidental damage protection, it is ANOTHER $200. I'm guessing you got a discount somewhere, I know Squaretrade often has 25% discounts going a few times a year. I would still prefer the Applecare + Statefarm.