One of my many jobs with my company is to create and put up signs. We have an unwritten policy to "stupid proof" our signs. (I know that sounds cruel; but that's just what we call it.) Meaning, if a sign is vague and it comes down from corporate in the system like that, we chuck it out and create our own. One of the things I've learned is you absolutely have to make sure that there is no question as to what the sign means.

This is one of those cases where someone didn't make a good, specific sign. If I was the store signer for that store, I would have made two signs: one for the pants and one for the shirts. Or I would have done this: "$19.99: individual tops and bottoms." Something like that. If it was for a set, then we would say it was for a set.

If I was you, I would have asked for clarfication of the sign. Do it politely. Sometimes associates just slap up signs without really taking the time to look at them. Or someone might think the sign is specific enough, but it really isn't. This is a way that those marketing associates can learn how to better do their job.

You could have politely pointed out that the sign is vague and you assumed (though you really shouldn't) that it was for sets. Perhaps the manager would have given you a discount, though forty dollars off is a hefty discount to take. I would have offered to give you one "set" for 19.99 and made you pay for the other two items at the correct price. The reason I think the manager shouldn't give you the price you wanted is because technically the sign IS correct. If the sign was wrong, then yeah, you should get what is says. But this is simply a case of vague signage.

Good luck.