Agree with TWT, 600-700 shrugs are not out of the question when training with serious intent. The traps are a very powerful short range muscle group and should be trained that way. I prefer a power rack, where some people have used up to 800-900lbs+ for partial reps in regular workouts. Than they drop the weight a couple of hundred and to do fuller range shrugs. (mini version of Wave training) I being one of those people in the past. I prefer a trap bar (more natural grip & the bar will not rub/drag against any part of the body) but can not slide on enough weight for the extra heavy stuff.
I think most guy's here, through no fault of their own, are not exposed to extra heavy lifting gyms. So when 600-700lb shrug are mentioned, they will have doubts. The BS flag is hoisted. Gold's, World's, etc can be good training places but most will not cater to the extreme heavy workouts that a lot of the smaller, independent gym's will. I train at a small, limited membership, converted three car garage gym that is more designed for power work. Heavy lifting happens (extreme to the average trainer who would train at a commercial chain gym) everyday in places like that. Really no big deal, that's just the way it is. We have a couple of 9ft bars for shrugging, Dl's, squats and such. Good Luck.