Front Tire Inside Wear - New Problem

I have a 2005 Prius with 177,000 miles. Over the last 14,000 miles (2 tire rotations) I have had significant tire wear on the inside of the front tires, particularly the driver's side. Tire Shop (Costco) recommended a front end alignment, which I got and everything was in the green (within specs). Now 6,000 miles later when I went back into Costco for a rotation they show me where the inside of the driver's side front tire is worn down, with the belt starting to show through. Similar, but not as bad on the passenger's side front and less, but still there on both rear tires. Not certain what the tire rotation pattern was. I had 36,000 miles on the tires, so wound up buying a new set.

Any suggestions on what might be causing this more recent tire wear? Can I fine tune the alignment so as to reduce/eliminate the inside wear?

Over the life of the car I have had gone through four sets of street tires for an average of about 36,000 miles per set. Original tires (19,000 miles), second set (Michelin X radial - 32,000 miles), third set (Michelin Energy Saver - 52,000 miles), Bridgestone Ecopia - 36,000 miles). Just put a new set of Bridgestone Ecopia's on at Costco, but they may not sell me any more tires unless I can solve the wear problem.

I solved a rear tire wear problem a long time ago with aftermarket shims being installed. I am good about rotating every 5-7000 miles and checking the air pressure. Because the tire dealer's do not like you to go outside the recommended pressures, I have stayed with 35/33. Just trying to understand what I can do to reduce this significant inside wear and get more miles out of my tires.