E filing costs and options

Hello- I am ready to e-file my taxes.  TT offers to file both federal and state and gives me the cost to file state.

If I file only federal now, and come back to file state later, will the cost be the same?  Or does this state filing cost only apply if I file both at the same time?  Maybe this is a bad approach, but I like to file my federal and get that accepted before filing state, since any mistakes on federal will affect my state return.   Thanks for any advice and insight!