You could expect the return package to weigh in at least 100 lbs. The M60s each weigh 47 lbs. each. Factor in packaging (which they come in, and which can be re-used for the retun trip,) and you're probably talking more like 125 lbs.

SO, then it depends on how you want to ship it and from where you'll be shipping it. Check out ups.com, fedex.com and usps.com for that information. You'd be in the best position to figure out how much this would cost.