When you consider an Ag Aircraft can go for $1million+, these drones are being sold by an Australian Distributor for $40k each with 8 batteries included so getting a bunch of them up at the same time wouldn't be a big stretch at all, not to mention the long term decrease in costs such as Maintenance, Fuel and Crew, you could easily convert a Pilot and an Ag Aircraft into 20 or 30 of these drones for hire. Develop a good truck to carry them and some ways to easily store and distribute batteries and liquids for when they return a crew of 2 can turn them around pretty damned quickly and cover a lot of hectares in a day. Being able to fly lower and having the down force of the props forcing the liquid down would mean they can probably take some slightly higher winds.
For those that have done ag, 1000L a load isn't unusual I believe but how much does your speed affect concentrations? My thinking is that by moving slower they might need lower dilutions. Of course it'll still be a big difference but still a difference that starts to shift the maths back. Of course there will be things that the real deal will do better for now but considering 10-20 years ago this was pie in the sky and now we have them being produced like this and getting better every year I think the smart companies will be looking to invest in this sort of tech sooner rather than later.