My gosh, if a builder wants to sell their amps at a premium, then for gosh sakes, sell your amp with premium tubes and make those your stock tubes. Showcase your amp with tubes that make you proud of your design efforts and nothing less.
Lamborghini doesn't outfit their "Lamborghini Huracan," with sub-par wheels on it. Their stock wheels are the car as well. The same should be with amps and their stock tubes.
but that wouldn't encourage you to roll tubes if you already have the best ones. Maybe having a maxed out option when buying would be better.