The airspace they fly through isn't a very nice place to be, so actually getting three of them to hit the tank may take more than three, or maybe three plus various systems to counter various other systems operated by the tank's friends. Air defense and electronic warfare equipment can be expensive and hard to produce.
Drones also haven't made anyone stop using tanks, which means they still need them for something important. If they get blown up more often you need an even bigger tank manufacturing industry making more, and countries with higher GDPs are pretty much always better at that.
Then we'll probably put anti-drone systems on the tanks and make them even more expensive. War is a rich man's game.
Well, in the case of the Lancet, at least at the moment it's decently safe for frontline use. There isn't a surefire way to stop them rn, except for jamming which has its own problems and using much more expensive systems to intercept, and its main advantage is that it has at least a 2x range improvement over an ATGM system, which is quite a bit.
The rest of your comment I agree with, but whilst people/countries are adapting/discovering what the actual value of tanks is vs what a drone offers you(and same for everything else, its a portfolio optimization problem really), the tanks do seem mispriced(at least the current generation). If all new tanks come with a comprehensive EW system the calculus will change again, but at least at the moment they seem to be overvalued.
The exact same thing applies to Russia as well, the entire Black Sea navy is basically useless due to rockets and maritime drones.
Drones also haven't made anyone stop using tanks, which means they still need them for something important. If they get blown up more often you need an even bigger tank manufacturing industry making more, and countries with higher GDPs are pretty much always better at that.
Then we'll probably put anti-drone systems on the tanks and make them even more expensive. War is a rich man's game.