.com is king and will be for a long time. The .org is intended for non-profits which of course don't have a lot of money to spend on a domain. Also, .net is the next best thing.
ABC.com $10k
ABC.net $2k
ABC.org $100
This is not set in stone as it is only ever worth what a buyer is willing to pay. Also, you need to evaluate the market demand for the domain. Some people are not thinking when they buy a domain and people believe others will like the same dome with a different extension. "If only it was that easy".
Good luck!