In remarks to Jake Blumgart writing for Next City, John Sisson, CEO of the Delaware Transit Corporation, says as part of the first official response to the #SEPTAWILM petition that doubling service will result in quintupling costs. That is an extraordinary claim, and nobody should take it at face value until they provide extraordinary evidence, including a complete breakdown of those numbers, before and after.
I’m not saying he’s lying. I’m saying that getting the $751,300/year figure of their current contract with SEPTA was like pulling teeth, and included no details. So there’s an airtight case that DTC is too opaque for a government agency, and a building, prima facie case that somebody there doesn’t know what the hell they’re doing.
Meanwhile, you should sign the #SEPTAWILM petition if you haven’t yet.
Sic Transit Philadelphia 
Sounds like he must be assuming DTC would have to pick up 100% of the operating costs (SEPTA would pay 0%, any federal or state funding would be $0), but even so … there are no additional infrastructure costs, little or no additional personnel costs, minimal additional maintenance costs to extend service.
Maybe he’s (intentionally?) forgetting that these trains are already getting to Marcus Hook on 100% SEPTA money and would continue to do so; and is trying to claim that in order to get additional Delaware service, DART would have to pay SEPTA to run additional trains for their entire Center City to Delaware route?
It doesn’t come across as needing a calculator; it comes across as a calculated attempt to completely squash the idea because he doesn’t want to do it for some reason having nothing to do with cost.