I have worked on several professional racing teams... first off it always costs more then you think, its one of those thinks that separates people who think they have a lot of money from people who actually have a lot of money. I have seen and worked with some very clever business men, who lost their ... when they tried to get into racing. Its more then just buying the bike, the tools, and hiring mechanics... you have to get the whole operation to and from every race (and testing) and take care of everyones food, travel, ect... then you have replacement parts, and other intangibles... so its one thing to start a team, its another thing to operate a team for an entire season.
My guess you could probably start a team for $250K, that should cover the bike and engine package, and tools & equipment. I think (someone correct me if I am wrong) the series helps with some of the logistics of moving the equipment around, I am sure there is a fee for that. Hiring personal, and moving them around the world for a season probably $1.5 million.