There's actually a reason they don't advertise an 'all in' cost -- "it varies by location".
There are Federal taxes, State-level taxes, and _municipal_ level taxes that one has to cope with. And usually several items of _each_ type.
The "Universal Service Fee" shouldn't apply if DSL is being added as a 'shared' service on the POTS pair. You're already paying that as part of the POTS service.
The 'package' deals are a whole lot messier, because you've got several kinds of service included. each with its _own_ bundle of taxes -- Not all taxes apply to all kinds of service in the bundle, and even when they do, they may be at different percentages depending on the particular service in the bundle.
In _broad_ terms, for POTS service, taxes can add around 20-25% to the 'base' billing, maybe even more. For DSL, there's a lot more variability -- some people quote 'all in' numbers; for those that don't, figure at least 5% tacked on. possibly as high at 20% (rare)
Call SBC and ask for the exact figures for _your_ address. If the front-line salesdroid can't come up with them, ask for a supervisor.
Then, to be a _real_ PITA, ask them for a -written- quote. MAILED, not e-mailed.