Sugar maple and Norway maple look a lot alike, but you can tell them from each other this way:
Pull a leaf off and look at the end of the stem. If the sap that oozes out is white, it is a Norway. Clear and it is not, and if the shape is the same probably a sugar. Around here, Norway maples are considered invasive and not allowed to be sold in stores. They grow fast, produce lots of seeds, and have poor structure in their growth habits. Some cities like them because they are pollution tolerant. Most often people plant them because when they are still allowed to be sold, they are cheap (since they grow fast, and make lots of seeds).
Because sugar maples grow slower, and are often considered more desirable, they can be more expensive. They can also be fussier about soil and water conditions, a little less drought tolerant than some.
I say pull a leaf off of each and look at the sap, it will at least tell you if he simply gave you the cheapest thing he could could get, a Norway maple, and hoped you'd not know better. If both trees have white sap, shake his hand, he did just what you asked...if they are both clear sap, then he at least got you close.