How much does BNSF flip cost?

Excuse me, could you please clarify what you mean by "BNSF flip cost"? Are you referring to a specific financial transaction or investment related to the BNSF Railway Company? If so, it's important to note that the cost of any financial transaction or investment can vary greatly depending on a number of factors, such as market conditions, the terms of the agreement, and the specific details of the transaction. Without more context, it's difficult to provide an accurate answer to your question. Could you please elaborate on what you're referring to?