Colt 1991a1

I'm trying to figure out the ballpark value to this pistol. A Colt 1991a1, it has some wear on the finish, Pachmayr grips (still have the original grips). I've added a match grade trigger and full length guide rod. It is one of the most accurate pistols I have ever fired. I've done some research online and found similar guns going for $900. I paid $600 for it about 15 years ago. Any help would be greatly appreciated.

NEW Colt 1991 models are selling sub $900, an older used ORM (Old Roll Mark) like yours with the bill board size roll mark sell for considerably less. It's worth about what you payed for it, $600.

In TX, for $600 I'd buy it immediately, and would look at it closely for $800-$900. This has to do with the orig grips, trigger, and guide rod - and how many rounds fired and overall condition.
I take into account in a private sale there is no sales tax or other transfer fees and so on.
Bottom line, I'd put it up for $900 and come down as appropriate.

The $600 that you paid for it 15 years ago, due to inflation only, has the same buying power as:

$857.54

The value in Colt 1911s is in the rarer models. That model is fairly common so they don't go for as much.