Jo Ann, I've had the same experience. It is very hard to resist those bargains, but after years of bargain shopping, I realize that if I buy a cheap plant in August, all I get is August and September out of it. A Two month annual. The plants I buy on sale in June, on the other hand, usually thrive through the summer and make it through the winter. The exception was last year, when we had such extreme heat starting in June, and no rain for several months.
We have a long fall season here, so local nurseries stay pretty stocked up into July. Box stores have plants until October. Sometimes I buy the 90% off plants and try to winter them over in my garage.
The sale right now at Santa Rosa is perfect for us--so many of their plants are very drought hardy. They have the best selection of grasses anywhere! The sedums they carry are the newer ones that stand up better. Sedums and grasses are beautiful plants for fall color.
I forgot about that, they had that last year! 
(sorry, forgot to tell you the plants) 
Especially with Echinacea if I can not get them in the ground by end of June losses are way to high.
