With the possibility of sounding overly idealistic:
I feel that anybody with pure and righteous intentions, who is motivated and desires to improve themselves in any way should be able to do so, regardless of their financial situation.
As one who does run a dojo,
First, before you make this proclamation, find me a space with no bills.
Second, invent a device that allows me to instantly detect all such students with such qualities that are worthy of a free ride. That includes them sticking around for years and paying back by teaching future generations for free, etc.
There is at least one thread on aikiweb that discusses this in much detail. I have actually had students that profess poverty to get a financial break that I later learned exaggerated their situation. Sad situation but it happens. As long as fees are within reason, I would say if it is really important to you, you will find a way to pay even it means a second job, etc. I am not terribly sympathetic. Learning aikido or any art/passion is not a right.
Now if you really want to talk about traditional budo, first go back one step from Aikido (not traditional), to Daito Ryu, my understanding is that Takeda Sensei charged per technique. It was also fortunate that M. Ueshiba Sensei had a wealthy family member to bankroll him, training with Takeda Sensei for an extended period of time meant housing and feeding him everyday.
Go back to really traditional, well you better be family or my clan, and the feudal system means in the clan the teacher got a healthy payment of rice per year.
IMO, these ideas of not compensating the teacher are not traditional at all.