Most AR15 barrels sell for over $200 new but, there are some selling for around $180 so if you are planning to use them for a build(not for a quick resale) then yes they could be a good deal IF they are new take offs or in good shape and have the twist rate you need to shoot the projectiles you plan to shoot. Some Colts are 12 twist and are really limited to 55gr and lighter bullets. If they are 9 twist then you could shoot up to 69gr Sierra's maybe even some 75gr, if they are 7 twist you could shoot up to 80gr bullets but some light(40gr and under) and thin jacketed varmint bullets may come apart at high velocity.
Make sure they are Colt, should be stamped on the barrel along with the twist rate and chamber. Colts can have a better resale value. If they are used then the price may be a little high.