Vakue is based on exact make, model, and condition. You gave us one of tthe three items we need to answer.
100 and up
about 599
About $300-350, depending on condition.
They are two different (but related) calibers of cartridges. The .270 is basically the 30-06 cartridge that has been necked down from .30 to .27 caliber. The "rate of twist" for the rifling will also be different, since you are shooting a skinnier, less heavy bullet.
50-125
Check
150 or so
10.99
$200-$250 new or $175 or less used
10-200 USD or so
About $285 at Gunsatcost.com
Depending on condition, from $100-200.