Any E911 feature is going to cost something, in the $0.89 to $1.99 per mo month range, this is on top of any per line/per month charges. This is so because providers of the service, evidently including VoIP providers,
collect a fee mandated by the FCC to fund the entire 911/E911 program in every county, city, township, across the country.
Plain old 911 can be setup at no cost, note without the "E," provided: 1) Your
PSAP has a seven digit or nine digit number that is answered as the equivalent to 911, and 2) you can configure your Obi to dial the seven or nine digit number when you dial 911. # 2) is easy to do and easy to test, multiple discussions on here of how to do it.
One more thing to consider. The next version of E911 is NG911 (Next Generation 9-1-1), it will incorporate the use of text, images, video (upload and link to YouTube?) and data. I'll guess the fee is not going away and if anything will increase.