Getting a suit altered can be as good as made-to-measure.
I was looking at several tailors that offer made-to-measure recently, where your suit is still made by machine, but uses specific measurements to create the template for that machine. It is incredibly unlikely that an off-the-peg suit will fit you perfectly, that your chest is bang on 40 inches, for example, and jacket and trouser waist fit the corresponding drop (the chest to trouser-waist difference, usually six inches on modern suits). So tailoring or made-to-measure are the only options if the suit is going to fit well.
But watch the number of measurements the tailor says he will take. If it is only seven or eight then there will be no difference between that and a tailored ready-to-wear suit – as you can easily have these seven or eight changes made yourself. When I asked the tailors how many measurements they took, it varied from eight to fourteen. And I decided that one ready-to-wear suit only needed a few adjustments.
I opted for an off-the-peg suit at Ralph Lauren with the trouser length, sleeve length and jacket waist adjusted. The adjustments are done at cost – £12 each.