I have older uninsulated duct work, that seems to be the killer. My last month bill was 2.25 per therm. And no,my electric bill is separate.
Unless you have a secret pipeline connected to CT or NYC, you get your NG from the same company I get mine: National Greed (aka National Grid, formerly KeySpan, formerly MarketSpan, formerly LILCO).
Our NG prices are surprisingly comparable to the rest of the country, unlike our electric rates (which contain the interest payments on a Nuke plant left stranded long ago).
Your calculation of $2.25 per therm is probably during your Summer use period when the $22/mo basic connection charge is skewing your minimal usage charge.
I have the same situation when I use 10-15 therms per month in the summer,
and use more like 150-200 therms in the winter per month.
If you look at your "year end" billing summary (balanced billing), or just add your full years Therm usage and compare to annual bills, you'll find a better $/therm number.
My calander 2012 costs were 1.46 $/Therm (used 937 therms).
My calander 2013 costs were 1.38 $/Therm (used 1028 therms).
The actual NG (fuel only) cost last winter were about 0.55 $/Therm, and dropped to about 0.35 $/Therm this past summer. Our major costs are in the Basic & the Delivery. The Taxes are remarkably reasonable.
For me the cost of pellet heat would be more expensive and more work, but I like to be diversified and I love the look & smell of a wood fire. Stuffing something in my "heat robbing" empty fireplace is also be a benefit.