The blockchain requires the witnesses to submit a price feed with the current STEEM price, so that it can properly calculate the appropriate size of the rewards pool, and how much STEEM to generate when users convert SBD to STEEM.
Your account operations are handled by the elected witnesses who are assigned the blocks, regardless of whether you voted for them or not.
Your witness votes will always be calculated using however much SP you have in your account at the current point in time.
@TimCliff, does voting for witnesses cost me any SP? For the first time about a day ago, I voted for 30 witnesses for Steemit and now I am reading what you are writing in this comment about the calculation of the SP for witness votes and I am not sure if that means that SP is taken out of my Steemit wallet to pay for witnesses or not. I would assume or hope not but better safe than sorry is my philosophy like @Stefan.Molyneux.
It does not cost SP to vote for witnesses.
Thanks.