These days you can purchase a suit almost anywhere, including Wal-Mart. But not all suits are created equal. Below you can compare the different sources of suits, their features, benefits, and prices.
I believe that the best value is in the third column. Here you get most of all of the benefits of a true bespoke suit at a fraction of the cost. If you're willing to shop around you can probably find a retailer with costs at or near those of upscale off-the-rack stores.