Now that REALLY stinks! Unfortunately, as stinky as it is, it very well may be correct. It isn't unusual for CS for one child to be anywhere from $600 - 1200 per month, if you make a decent salary.
Have you done the calculations yourself? There is a CS calculator at the NH web site so you can calculate it yourself. I just checked the guidleines and it reads 25% of net income. Actually that isn't too bad as a number of states calculate it on GROSS income. Does your ex work? If she does you might want to check and see if HER income has been included in the calculation ... or if she is voluntarily unemployed you can have her income imputed - it "might" make it worse for you though, so you need to be careful.
The link for NH statutes is
[A HREF=http://www.gencourt.state.nh.us/rsa/html/XLIII/458-C/458-C-3.htm]Section 458:3 Child Support Guidelines[/A]
There is further information at
[A HREF=http://www.gencourt.state.nh.us/rsa/html/indexes/458-C.html]New Hampshire General Court CS Guidelines[/A]
Good luck and post further information - perhaps others can help you.