baba metzia 108b - doing what is straight and good

rashi holds that v'asisa hayashar v'hatov is the buyers obligation, not the seller. based on this rashi explains that there is no valid complaint against one who sellsto a goy since a goy is not required in v'asisa hayashar v'hatov. but rashi struggles with trying to understand the gemara that says a talmid chochom comes before a neighbor. if it would be a mitzvah of v'asisa hayashar v'hatov on the seller it is possible that his mitzah to honor a talmid chochom would take priority over v'asisa hayashar v'hatov. but sincecit is a mitzvah on the buyer, it doesn't make sense to prioritize talmid chochom because he is just as chayev in v'asisa hayashar v'hatov as anyone else. therefore rashi and tosfos explain the gemra to be where v'asisa hayashar v'hatov because both r neighbors or both aren't neighbors, and the whole discussion is an issue of prioritizing which is indeed incumbent on the seller and therefore makes sense for a talmid chochom to get priority.