I bought a 700 VTR (Varmint Tatical Rifle) in .308 a few years ago and I really like it. It has a 20" heavy weight barrel and an all weather stock. It has two front swivel studs so you can add both a sling and a bi-pod.
It was about $650 as I remember. There are probably less expensive models but I really like the VTR. It shoots about a minute of angle with Remington factory 150 grain PSP Core Lokt's at 100 yds.
If you are looking for a lower priced used 700, there are a lot of 22" bbl BDL models in 30-06 out there. The 30-06 is a great deer cartridge.
I think that most of the .308 700's were the higher priced grade varmint and tactical models.
The Model 700 Carbine is it's own model, they're fairly rare, but they are out there. A guy that used to collect them used to transfer all of them from a store I worked for and I used to do his paperwork. So, I talked to him and used to ask him what he paid for them, and it really varied. He was the president of a bank, and he didn't really care what he paid for them, he used to buy whatever he found in 700 Carbines, he paid anywhere from $350-$700 dollars, the upper end were some that were in pristine condition. He told me some chamberings were more rare than others, but I do not believe the .308 was one of them, I could be wrong, though. I think the 350-600 range is about fair depending on condition, though.