Questions & Answers about Puer quaerit cur textor purpuram tanti pretii vendat.
Because cur textor purpuram tanti pretii vendat is an indirect question after quaerit.
- Direct question: Cur textor purpuram tanti pretii vendit? = Why does the weaver sell ... ?
- Indirect question: Puer quaerit cur textor ... vendat. = The boy asks why the weaver sells ...
In Latin, indirect questions normally take the subjunctive.
No. Here the subjunctive does not add that kind of English meaning.
In this sentence, vendat is subjunctive simply because it is inside an indirect question introduced by cur after quaerit. So you should understand it as ordinary sells / is selling, not as may sell.