Salespeople generally convince people to exchange money for commodities (completing the C-M-C circuit for capital accumulation) and bargain to make the customer pay as much as they reasonably can for commission. We would be engaging in commodity fetishism to just wave off the marketing and sales department as "not real jobs." One could argue that while value derives from "useful labor," less time that a salesperson/marketer spends working is actually useful or their labor is generally less useful. Following that line of thought, some could argue that they could have a less "prole" background. That's kind of irrelevant though. The big focus, however, is that some of their goals are more aligned with the capitalist class. Salespeople will want to sell commodities at higher prices for more of their commission, screwing over more customers on behalf of profits. Car salespeople in Amerikkka, for example, would definitely fit the role of "labor aristocrat." They are one of the largest, most conservative groups in America that want more car-dependent infrastructure and lower wages so that they might have a larger slice of the pie in the inflated exchange of commodities. Depending on the position, role, and most importantly how much they are aligned with the capitalist class's goals, or their class interests, sales and marketing people could be proles or part of the labor aristocracy.

You wouldn't really be a class traitor for earning more than whoever made the thing you are selling though: just by working against your class interests.