I have some 15 round usgi m1 carbine mags that a friend would like to purchase from me, but I do not know what a fair price would be. I have not found any for sale anywhere to get an idea what they are going for so I thought I would ask here. Does anybody know what I should be asking for them? Any help would be appreciated.

What manufacturer?  I'd say around $20, give or take a few bucks.

the only mag I looked at before I gave them to my friend to look at was stamped with a u, I assume that is underwood? but not sure.

Tell your friend he can get new 15 round KCI Mags (as good as USGI) for about 11 bucks. 30 rounders go for about 13 bucks.

What type of font was the U?  The modern Korean mags are stamped with a simple U.  They used to be about $10.  More recently, I have seen some vendors charging much more.  Although I have never had a problem with them, I throw a couple in when I sell a carbine.  I bought ten or fifteen when they were first came out and were cheap.  When you bought the bulk pack, they came out to something like $8 each.

I have picked up USGI ones for $15 to $20.  Some go for $40, but they are genuine USGI still in wrap.  I think places like Numrich have prices listed by manufacturer stamp.

Are the kci mags actually decent? First time ive heard that

They work.  There was a bad batch where the locking tabs would break off, but I haven't heard of it happening in a while.  I think some people replace the magazine springs, because the KCI ones feel soft compared to USGI, but I have never had a function problem out of them.  They are just easier to load.

This other company sells repros for a decent price.  I have heard they work well.  They look like Koreans but these guys claim they make them.

http://www.keepshooting.com/firearm-accessories/m1-carbine-parts/m1-carbine-magazines

thank you. as far as the font,I am not sure about that. I do know I bought them 15 plus years ago, I think before the Korean mags were around. I gave them to my friend to look at so I cannot check them now. I do not want to rip him off so I will probably tell him around $15 each.