FYI--the USCIS has proposed an increase to certain fees
There is no date scheduled yet for the fee hike to go into effect nor it positive that the fees will be raised BUT the I-600A will increase to $525 (from $460 currently).
http://uscis.gov/graphics/index.htm The announcment is on the main page of their website (has been since Feb)
The fee for filing an N-600 on the behalf of an adopted child will raise to $200 (this is the COC form--for a non adopted child it may go up to $240) (If your child comes home after Jan 20 of this year on an IR-3 visa you don't have to worry about this one)
Fingerprint fees which are listed as biometric I believe may go from $50 to $70
From this point on (and I'm not sure when they think these new fees will go into effect) fees will increase based on inflation each year (starting in Oct of 2005)
http://uscis.gov/graphics/lawsregs/04-2290.pdf is the full report
In theory you have 1 year to submit your homestudy from the time you put in your I-600A although many offices no longer accept your form without a homestudy. SO technically you could avoid the increase by submitting your form early however then the gov't have your money for no good reason