No product or company that I know of includes taxes in their advertised prices - that's to be expected.
The thing to remember about "introductory offers," of course, is that they expire, and people forget to monitor their bills. When I switched from Comcast to DirecTV, I figured out what the price would be post-intro-offer, and it was still a huge savings over Comcast for equal packages. But even I got caught. I tried to cancel the "free" Starz package, but every time I would call to cancel, they kept extending the free offer. After about 3 extensions, I forgot, and ended up paying $10 extra per month for this package I never use.
So lesson learned - when they offer to extend, I will just cancel.