Gov't issue, huh? And which gov't exactly was this rifle "issued" to "back in the day?"

As it sits now...it was NOT issued to ANY government (at least in the US) in that condition.
Scope and mount are both JUNK! That's the Springfield Armory mount (two-screw...maybe Gen II...hard to tell from that pic) which is notoriously poor compared to higher quality mounts like Sadlak, etc. The scopes, while some people seem to have good luck with them...are generally NOT good. The glass is pretty sub-par (hazzy, yellowish tint on some models), the adjustments aren't always true/accurate, but they are FFP which is nice even for an otherwise garbage optic. They were made for SAI by Hakko in Japan who still services the scopes if there is a problem with them. Service is iffy at best and generally isn't worth the time/effort/frustration to deal with it. I can't tell if the bipod is an original or a cheap, ChiCom knockoff.
Nothing about that rifle is "sniper" or even "sniperish" in fact. The awesome "6-digit" serial number you seem to be basing your claims (or the seller is basing his claims) on it being "government issue back in the day" doesn't mean squat in terms of its previous "service" and in fact, it hasn't likely EVER served anything except on the civilian side of the market (i.e. - if its as SAI receiver, a 6-digit serial would be expected and hardly "old" by any measure). Since you likely have the serial number or pics of it, you can request info direct from SAI about the "history" of the rifle in terms of how it left Springfield (i.e. - bare receiver, barreled action, complete rifle and if so, the configuration it shipped in, etc.). If you want to provide the serial range, such as 123xxx, or a pic of the receiver heel (with all or at least the first 3-4 numbers of the serial) then we can likely get you in the ballpark as to when it was actually produced, but SAI can give you the specifics.
At present...$4500 is WAY out of line based on the limited data you have provided thus far in the condition the rifle at least appears to be sitting in now. More info and we can likely get you a little better idea of what you can expect to pay, but I wouldn't piss on that rifle if it was on fire at $4500.
