Yes, it is. They don't have to sell it to you at all. There is nothing in the law that forces them to sell anything to you. In fact, they are NOT selling it to you. They are essentially selling you the right to right to USE something they own with certain limits they set.
The government does not have the right to let me worship God... that is a Right reserved to me. But I do not have the RIGHT to take something that belongs to my neighbor either. My neighbor does have the right to let me use something that he owns and retains ownership to... that's his right as well. I thank him by paying him for the privilege... or let him use something that I own in exchange.
Not much point in writing the software if you're not going to distribute it.
But I do not have the RIGHT to take something that belongs to my neighbor either.
But the developers don't have a natural right to the software, unlike the natural right your neighbor has to his property. The software belongs to everyone by default, but the Constitution allows for a limited monopoly of rights solely for the purpose of advancing the arts and sciences.
Thus, they can tell me all day long that I can't re-sell or make backup copies of software, but the right to tell me that wasn't granted to them by copyright. Any extension of power beyond copyright that they try to grab with a EULA is by definition invalid, because copyright is what gives them the right to say anything in the first place.