I'm going to have to disagree with most of the responses so far. I think a sensei has the right to insist that you buy from him. I'm not saying he should, but he has a right to. It's his dojo. He has expenses to cover. He bases his rates on having equipment sales. He's responsible for the safety of his students. If he sells you a product, he knows where it came from. Your sensei's markup does seem pretty high, but, maybe that's partially offset by a better guarantee or return policy. What if it doesn't fit right? Will your sensei exchange it at no extra charge? What if the sole starts to peel away after a month? Do you trust him to take care of you? And if you attend his classes, aren't you agreeing to follow his rules? If you can't, maybe you should find another dojo. I'm not a sensei. I'm in martial arts supply, so maybe I'm biased. I've spoken to a lot of our customers about this. Few require that students buy from them. Of those that do, they tend to take it very seriously. I've had customers refuse to let their students use equipment purchased from outside sources. Whichever way you decide, I hope it works out for you.