Roughly, from what I can find around the price is roughly $1,600 for the M1A. Extrapolating Gurps rules x 1.25 to get the value of Military Version.
My attention is drawn because I favor the G3 as a battle rifle. Quick scans anecdotal reviews come up the same. Strangely, the weight is glaring
G3 vs M14
Dmg 23 vs 24
Range 800/3750 vs 1000/4000
RoF 10 vs 12
Wt. 11.4/1.7 vs 10.9 / 1.6
Cost $1500/$35 vs $600/$31
In the wiki and gun sites
Note: clearly the 11.4 is 9.7+1.7. So they forgot to subtract the magazine weight.
If the Price of the m14 vs the FAl and the G3 were true then they would be the most common battle rifle around the world. Especially in poorer countries!
I agree with the damage since the G3 does have 17" barrel vs the m14's 20" a 1pt difference, which in gurps is exponential.
Having cleared this matter up. in a International Campaign, the G3 is the cheapest but lowest performing rifle among the stats I cannot verify for myself. Anyway 2,000-1500 sounds about right for battle rifle costs.
After had the chance to compare GURPS and Mongoose traveller, I like they graininess and detail of GURPS more. I can put in analogs of Modern rifles easily into the setting.
Injecting a little future-"realism" I can also make some of the battle rifles in bullpup constructions. Removing the stock from the full length is a BIG advantage when firing from cover. I should be applying half bulk penalty for weapons firing from tight cover in seconds or to hit. There is also the problem of left hand or right hand cover, which complicates the matter. Maybe a simple and fast way to adjudicate this is having to roll "cover traits" instantly and mark it in a post it.