His reported 5-year, $44.5 million deal makes him the highest paid center in the NFL. That's an average of $9 million a year which is extremely high for a center, but the Raiders had to bid high to make sure they got their man. After all, they had lost out on several other top free agent targets including Randall Cobb (re-signed in Green Bay) and Ndamukong Suh (signed monster deal in Miami).
Hudson was among the top five free agents set to hit the market at any position. With the Raiders letting Stefen Wisniewski leave as a free agent, Hudson was considered the one player on the market who would be a marked upgrade at the position. It's a big win for a team that really needed a win.
The Raiders have a lot of money to spend this free agency and had yet to find a place to spend it. This is the first big signing that would make dent in their $63 million in cap money available.