I have the opportunity to buy a KSP issued and marked G27 (gen 4, night sights) like new low round count for $400 from a state trooper friend of mine. Is this a good deal outside of just being a good shape used g27?

I've seen worse, but you're really just paying for a laser engraving with the KSP logo.  

Gen4 small frame guns with GNS are $455 IIRC with credentials.

That is a good price and considering G22 mags are pretty well available for $14-15, I'd jump on it.  Carry 9-10+1 and have a 15rd reload.

You could judge the age of the night sights by the S/N and the higher the lettering, the newer the gun is.  You'd probably have 7-8 years of good use out of the sights.

I literally don't even want a glock, I just think it would be really need to have something that you cant just go out and buy anywhere, to a have a piece of state history, unique "cool via gun friends/range buddy" factor, and I know the money is going to a good cause.

It'll make a decent suppressor host too.  180gr .40 is really quiet.  My 22 and 35 are my favorite guns to shoot with my .45 silencer.

Most KSP marked guns bring a premium to collectors, especially the S&W wheel guns, 10mm autos and the older long guns.  Please let me know if you run across any!  
The Glocks not so much.  There will be twice as many Gen4s on the used compared to any other KSP pistols, the warranty trade-ins (rust on just a few so Glock swapped them out for new ones) and now the transition to 9mm will put another 1200 or so on the used market.  Most any Glock is worth $400, so I would say pick it up.

The logo guns sort of have a value but pretty much for the reason you stated, a piece of history.  No real collectors value, just a unique gun.  Centerfire Systems is selling the same gun for $399, not sure if it has the logo or not, some do from different agencies though.  https://www.centerfiresystems.com/p-7142-glock-27-40-sw-police-trade-in.aspx

I have a Glock 22 that came from the Detroit Police Department, from when I lived in Michigan.  The serial number started with DPD.  Unfortunately the slide rails broke and the replacement lower from Glock had a different serial number.  The slide is clearly labeled though.  Shortly after I bought it the DPD decided that officers could no longer keep their duty guns when they left.  That was back when Rosie was trying to put Kmart out of business due to Columbine.

Don't forget, the fact that it should have been well maintained, relatively low round count, and not be "hot" adds value too.

That isn't terribly much more than the officers could buy them for themselves.  Those guns at the earliest were issued in 2012.  Should be in excellent shape and low round count unless he was a big shooter (even then, its the 27, nobody shoots that one much).  

I'd say that's a solid FO.  Most of the frames on them have "patent pending" on them since they were very early gen 4 guns

Feel free if you have any questions about KSP guns.  I collect them.  And if I don't know the answer I can text a guy I know that far exceeds my knowledge

He's taking a $9.00 loss selling it to you for that price. Buy back price after transitions was $409 for the 27's. Just FYI. If you want the seal, probably won't get it any cheaper.

Hell, the 27's were going for $350 and the 35's for $400 less than a year ago. By the time I decided to buy a 35 they were all gone from Armslist and the local dealers and the 27's took months to finally disappear.

Wish I would have kept my KSP marked Smith Model 60

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