I will agree with the fact that it could be an issue for small business. It depends upon implementation (which I have admittedly not look closely at in this matter). However, in my experience with the ADA (which is what I was thinking more in terms of), it causes less financial difficulty than you imply. It commonly breaks down to a matter of reasonable accommodations. Therefore, I would assume (maybe inappropriately) that if implemented reasonably, it should not be any more problematic than the original ADA.
On the basis of money being spent on accommodations for the disabled, we are talking about 1 in 5 Americans (seems to be the consensus on Google) or more than 40 million (from the article). That seems like a fairly large group, when considering the diversity of the United States. Your example with tennis is not particularly fair. The internet is not some tangential leisure activity. Many peoples' livelihoods depend upon the internet. If we followed the free market from accessibility, then many would be stuck in their homes, without means to do otherwise. If you are fine with condemning that many people to such a fine, that is fine, but I'm not.
Again, I encourage you to really consider the challenges of being disabled. I don't think you fully appreciate it. I don't think I fully appreciate it either, but I can say from my experience at least how hard it is. I'm just thankful there is some chance at normalcy from some.