First, an example: “The vase sells at around $500.” A glance at the phrase might not cause a person to pause. It doesn’t sound all that wrong, does it? Perhaps not.
A secondary glance might cause a person to pause, particularly if that person knows her prepositions. The sentence contains two prepositions, “at” and “around.” A little awkward to be certain, and most definitely wordy. More worrisome, though, is that the two prepositions mean different things.
“At” suggests an exact amount. If the vase sells at $500, it sells at $500. No more, no less. “Around” is an approximation. If the vase sells around $500, it might sell for a bit more or a bit less. Who’s to say except the person selling the vase? That person must make a choice, and it’s dependent upon whether the vase sells for $500. If it does, the person must choose “at.” If it doesn’t, the person is free to use “around.” The person is not free to use both words; doing so results in a crowded, confusing sentence.