There are different calibers of mortar shells, bigger size has more range and power.
I think author of the article has cheated by not specifying the caliber, because a 155mm artillery shell cost is more than a $1000, precision guided one cost is tens of thousands. While a drone capable of reaching 10km+ costs less than $1000, without payload.
Why are artillery rounds so expensive ? Is it the raw materials ? Is it the precision of machining ? Is it because of what's required to make the entire process safe for workers ?
Of course they are less precise. And in most cases, they need quite a few rounds to adjust their aim at the target, so his comparaison was already stupid unfair.
He takes into account all the drones that don't work and then goes on and pretends artillery is 100% accurate and has an absurdly low cost (at the price he is quoting, they are basically sending grenades).
Let's not even discuss moving target or penetrating inside fortified targets which mortar will never be able to do.
