There's a very interesting fallacy at play here. It's true that Ukraine is doing absolutely amazing and ingenious things on a shoestring budget across all military domains. It's also true that the armed forces of other world powers have a lot to learn from them, especially when it comes to drone warfare.
The fallacy comes in when blindly transferring these lessons to other wars and other armies.
In a perfect world with unlimited production and budgets, Ukraine would love to use Patriot or SAMP/T to shoot down every slow moving drone. In the real world, they make do with what they have, because the alternative is defeat and annihilation.
Ukraine is using propeller trainer planes to shoot down Russian drones because they have them and they can be quickly modified for the mission. That doesn't mean that an air force starting with a clean slate would prefer to use a cheap propeller plane in an anti-drone role. Instead, given enough time and budget, they'd probably prefer to build a custom-designed, more expensive and more capable solution, which still lands in a better spot on the shot exchange curve than Patriot vs Shahed. Think interceptor drone (which are usually several times more expensive and capable than their targets, but that's air defense) or 21st century gun systems.
Ukraine is a post Soviet state with a huge stockpile, engaged in a drawn out attritional defensive conflict where neither side has claimed air superiority. They have no choice but to be efficient, and to make everything they have go as far as they can. From an economic point of view, the USA can afford to be less efficient when fighting into Iran.
For the USA, shot exchange as an economic problem is mostly theoretical. The real problem is supply exhaustion. It doesn't matter if the air defense interceptors cost $10,000 or $10,000,000 if the total stockpile and yearly production capacity of them is only enough to fight for 3 months.