Noble Pepper, he does not have " sucker written all over his face" His
aluminum doors have probably a total R value of less than 1 , with high
air infiltration. Anderson which I have have apx 3.5R and have maybe the
best made glass in the industry. I paid 800 per slider and 750 per
install, a area standard price. Sure you can go cheap, but you get what
you pay for.
On the instal be sure You check Plumb, Level, and Square, before you
pay!! If you are more than 1/8" out you have No factory Warranty. The
quality of the install- installer is far more important than going cheap
and saving a buck.
My installer was a hack, grease, dirt on the wood, and out of square,
locks not set right. Luckily I caught his mistakes before he left. Be
sure the instaler has instaled Andersons, and call these people.