The $30 million means that the Rangers will effectively be paying Prince $138 million over the next 7 years. Fielder is coming off his worst season since 2006, putting up a .358 wOBA and a .279/.362/.457 slash line. Fielder will likely see a jump in his stats moving to the fair smaller park in Arlington. I'm not sure I'd want to have Fielder on my team in 2020 when he will be 36 and likely somewhere north of 300 pounds.
The Rangers almost had to move Kinsler, since they gave Elvis Andrus a big contract that runs til 2022, with an option for 2023 (doesn't that sound a long way off) and Jurickson Profar needing a middle infield spot to play. Kinsler is owed $57 million over the rest of his contract that ends after the 2017 season.
Update: I missed something interesting. Kinsler has hit .304/.387/.511 at home over his career, but just .242/.312/.399 on the road. I wonder if that is a home cooking thing, or if Arlington is just a good place for him to hit.