I do not think the rust is all that bad -- superficial, IMHO.
The bike is clearly not, as claimed, a 2018 Atlantis -- it is older -- looks like an early 2000s Toyo bike to me. Seller says it is a 53cm. The seller also says they're the second owner, that they paid between $1.2 and $1.5k for it (odd to have such a range).
Julian Westerhout
Bloomington, Il
I think a careful inspection and some probing questions might be warranted.