I don't think they are as high as they used to be, they've improved their recipes over the years. I just scrolled down the list of healthy choice dinners on their site and they all had 600mg (or just under it) per meal, and this is reasonable. By comparison, there are 500mg of sodium in a 1/4 tsp serving of salt.
Healthy individuals should limit sodium to 2,300 mg per day, but you should also get at least 1,500 mg. Too much sodium can cause you to retain water, but not enough sodium can be damaging to your health. If you don't retain ANY water then you become dehydrated, so it's important to get enough sodium. Balance is the key. Drink plenty of water throughout the day to keep your body flushed of excess water, and try not to exceed the daily limit of 2,400 mg.
I agree with Susan that preparing our own food helps us keep better control, and it tastes better, too
Many processed meals taste too salty to me, even if it's just 600mg salt in the meal. Maybe it's due to all of the other chemicals and preservatives that are in there, I don't know.