The German Motorrad magazin tested biker jeans recently.
Cheap biker jeans failed on the connection parts first (seam etc.). High quality (and usually expensive) biker jeans had similar protection as textile gear for bikes - surprisingly good.
They also tested jeans with standard denim, without the special material and protectors. Result was terrible.
No surprise that standard jeans may look good, but are not safe to protect us in case of an accident or even relatively harmless drops.
Current: 2014 BMW K1600 GTL Exclusive
2012 Silver BMW C650 GT
History: HD Ultra Classic CVO, HD Heritage Softail, Honda 1100 ACE, Honda Spacy 125, Suzuki XT 125, Puch Maxi
Our most frequent mistake is to believe that others think the same as we do.