Going to the Musjid after playing sports

Q: I came to know that wearing half sleeves shirt while performing Salaah is Maqrooh. I want ask that I go for squash daily from asr to maghrib so I wear half sleeves so I can play and it is very difficult to first pray in full sleeves than go back home and prepare for Squash. I also want to know that as squash makes you sweat, so can I pray in sweaty shirts as well as half sleeves?

Bargaining

Q: A man buys something whether it is clothes or mobile phone or anything. Will he have to bargain for the thing he's buying or not ? If a person is rich and he doesn't matter about price he just buys the thing as it rates will it be okay according to Sharia?