You ALWAYS want to make sure that you go through with the IPASS transponder. IPASS does not tell you this, but they will charge you the non-IPASS cash rate (double) if you do not have your transponder while going through IPASS, even if you are an IPASS customer.
Otherwise, no one would ever carry the transponder and just have the camera take a photo and then charge your account, which takes time and money.
IPASS got me before on this and the CSR would not give me the IPASS rate on my toll violations, even after I talked with their manager. This was after I received a violation notice of over $1,000 and about $70 in tolls (would have been $35 with the IPASS rate) going back ust shy of two years.
IPASS will catch-up to everyone eventually... another reason why I can't stand the state sometimes.