To me it's pretty logical they're not doing this out of love for mankind.
Schools sell merchandise at a slightly higher price, in order to bring money into the school. Monthly rent doesn't take care of itself, and I highly doubt that the electric company and water works will decide not to charge you anything.
A school isn't going to be any good to anyone, if it goes out of business.
Sure, you could probably buy your own uniforms from the usual bulk sources (AWMA, Century, etc), and save a few bucks. However, the school's owner would probably benefit a lot more, if you simply bought from him / her at that slightly elevated price. While it's certainly true that as a beginner, it's more of a matter of "what can the school do for me," as you become more advanced, it also becomes a matter of "what can I do for the school."
One school even wrote that you probably need more than 1 set of uniform cause during training you sweat a lot.
That's quite a valid point.
How silly is this? Ever heard of washing machines? Why do I need 3 pairs or more when I can just wash the stuff after a training?
It's not silly at all. I actually have 3 gi's that I use, so that I don't have to fire up the washing machine after every day. If you had to use the washing machine every day, that would get quite expensive, since I'm pretty sure that you're not going to waste a laundry cycle on only one uniform. This is, of course, assuming that you have your own washing machine. Otherwise, if you had to go to the coin laundry every day, you'd be burning through a lot more money than what you would had you bought more than one uniform.
This is just plain silly.
No, it's simply logical and practical. I'm going to be a bit blunt here and simply suggest that you do the math. You will see that I am right.
Yeah, I'll directly buy 10 pairs. No wait, better make it 15. Do you accept credit card?
You're not going to win any appreciable level of sympathy here, especially with your exaggerated statements.
Many of the folks in this community are advanced practitioners, who have been at it for decades. They have an idea of what it takes to operate a school, and that it's not all daisies and roses.