I'm not sure what you're saying here, it doesn't seem related to what was said before.
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> So you get great tool for detecting these issues in the future at low cost.
Detecting issues doesn't stop the issues getting created in the first place.
The goal should have always been to make the issues impossible in the first place.
> Without AI the cost wouldn’t really decrease with time.
The cost of what? AI has a front-loaded cost, just like producing better tooling.
> And also it costs me 200$ now to find these bugs. I don’t think I could hire software engineer for that much.
Tooling that prevents the bugs in the first place is effectively free once it has already been made.
> Tooling that prevents the bugs in the first place is effectively free once it has already been made.
Surely you understand that such tooling is basically impossible to create and even if it was impossible it would be so horrendously expensive and hard to implement that AI would actually turn out to be cheaper. Under the false assumption that such tools could be produced you are right, but that assumption is absurd.