What do you mean by "service"? Yes, you still have to pay for your programming package. But all other fees (DVR service, hardware rent/lease) go away entirely.

For example, my cable company charges $20 for DVR service plus $7 for each box. So my 4 TV system would normally cost $48 in fees alone.

With Tivo, there are two scenarios. If I have subscription service on my main DVR plus 3 Minis, then my fees would be $15 paid to Tivo and $2 paid to my cable company for the cable card for a grand total of $17 (Minis never have a monthly fee). If my main DVR has lifetime service, the my grand total is $2 (Minis include lifetime service for free). I have lifetime, so my monthly savings is $46 (~$550/year). That pays for my main DVR with lifetime ($300) plus 2.5 Minis. The other 1.5 Minis are paid for 3 months later. So beginning in month 16, I save $46/month.

I think Comcast actually gives you a credit for using a cable card. So you actually make money by using Tivo.