I have never bought 5.56x45mm ammunition in my life and so I'm not as well versed on fair prices as I would be for comblock ammo. Would you guys and gals pay $180 for 420 rounds of M855 that came on stripper clips and inside what looks to be a steel ammo can? The product in question is the following one:
http://sgammo.com/product/223-556mm-ammo/420-round-can-556-mm-xm855-lc1ac1-lake-city-m855-green-tip-ammo-ar15-stripper
I buy a lot of ammo from SGAmmo. Generally the best prices on the internet and I like that they tell you shipping up front. I've also fed my DDM4 mainly LC brass. That said, 46 cpr delivered is getting pricy. Until recently 42cpr delivered was good. The factory packed .30 cal ammo can with ammo on strippers is a bonus so I wouldn't hesitate much if I didn't have any M855 on hand. These .30 cal cans are a very handy size and weight if you want an easily mobile source of cartridges.
Their bulk Israeli IMI M855 seems like a great value. I haven't tried it yet but if I wasn't stocked I would.
SGAmmo's webpage is my first stop whenever I'm buying the comblock calibers. They're good people running a good family owned business. I was looking at the Israeli stuff, too, but that ammo can caught my eye, lol.