Contact the Municipal Sewer Authority. They're usually located in the Municipal Building.
I live in SE PA and the tapping fee is $2,400 (a one-time fee.) Beyond that, the homeowner pays to run the waste line from the tap to wherever you 'end'. Sometimes, you can couple the line coming from the street to where the line in the septic tank 'meets' the tank. It can save some $$$. If you can't do that, or the septic line is FURTHER from the house, or the Municipality won't allow you to make this particular hook-up, you would obviously have to go right into the house w/the line. I can't tell you what the cost is for laying the line because, these days, they're using flexible lines as well as PVC as well as cast. AT the same time, they could be different diameters depending if they're under pressure or gravity or whatever. Usually, when hookups are done on a large scale, the Municipality 'collects' the names of a few Plumbers that are interested in the work and they pass that info to the homeowners. See if such a list exists.
DH gives a good idea - Deduct the cost of the hookup from the bid price. Either talk to the homeowners who are already hooked up (for what they paid), or get that list and see if you can get an idea of the cost. Do realize that unless you get someone to visit your property, you'll only have a 'good idea' of the price. I don't know who you've talking to but it sounds like you're not talking to the right people. Again, ask for the Sewer Authority folks. Maybe you or someone has to pay a visit in person. In my Municipality, 1 person runs the office.