How much do automatic sliding glass doors cost?
20 foot storefront, 8 foot high, double-sliding glass doors
These sites may help you http://www.homedepot.com/webapp/catalog/servlet/Search?storeId=10051&langId=-1&catalogId=10053&keyword=Double+sliding%20glass%20doors&Ns=None&Ntpr=1&Ntpc=1&selectedCatgry=Search+All http://www.marvin.com/patio-doors/
I just had a friend look into something similar and I think he said it was around $1,000.00 per square foot (that was installation also). Don't know if that's accurate but that's what he told me.