How to tell if sausage package swollen or just taut
If you can tell us, "They smell fine" then you have since opened the package. It is not uncommon for air to be trapped in those plastic wrap trays. Since we can't see or smell it the only way to answer your question is: "Is $4.00 worth of sausage worth a few extra trips to the bathroom?" If it smells 'ok' then it is unlikely to be 'dangerous' ... but only you can make that call.