I contend that you do not in fact value art because of the effort involved, because I am confident this is not a metric you apply to anything else.
Just saying it doesn't make it true.
You don't value wars of aggression, for example, even though they generally involve a titanic amount of effort.
I do. I have a nice collection of WWI and WWII military models which I admire for the 'art'. Without those wars of aggression I wouldn't have that. I have to keep reminding myself of the purpose of that tech and the enormous suffering it caused, yet that doesn't diminish its beauty in my eye. Millions of military modellers around the world face the same dilemma.
I'm also confident that your valuation of a given work of art is not actually contingent on the amount of effort it took to produce.
Another bare assertion. So when people spend good money to see a live concert, only to find the performers lip-syncing to prerecorded music and the instruments not plugged in, you think they don't care? Anyone who has tried to play eg. a guitar or paint in oils knows the amount of effort required to get good results. The appreciation isn't just about the art itself, but the efforts of the people who created it. We praise them not just for the end result, but for bringing us joy and contributing to society, which encourages them to do more. This is a large part of what makes us successful as individuals and as a species.
You may say that AI can produce the same result so what's the difference, but it
can't. The AI isn't actually creating art, it's stealing from the people who did. And because AI is a machine, not a human, it doesn't add anything human to it. All it does is ape human style with no intelligence, no emotion and no meaning. There is no mind behind it to identify with.
So what's the problem, you say, if people still enjoy it? The problem is that it displaces art made by humans and lowers the perceived value of art in general, making it harder for artists to live. AI doesn't innovate, so we don't get anything truly new or interesting. Instead of only 90% of it being 'crap', 99.9% is, drowning out the 0.1% of art still made by humans. This will eventually lead to a breakdown of society as we become mere consumers of meaningless dross.
Separately, I think that would be a terrible metric for valuing art. Breakdancing is certainly an art from. Rachel Gunn certainly put some effort into breakdancing. But nobody in the world values her art, no matter how hard she worked on it. Not even you.
The exception proves the rule. If nobody ever valued effort you wouldn't have to come up with an example where they don't.