This is just silly and unrealistic. You have completely neglected detection and targeting issues. What types of sensors would be needed? What field of view do they have? How much power do they consume? How much does that sensor suite cost?
You haven't actually answered anything. Sure it's theoretically possible to build a large, fast UCAV with advanced sensors. But it will be nearly as expensive as current manned fighters, and still not very useful at countering small, low-altitude drones.
Which is why I (a few posts up) argued that several size categories of drones are needed.
To counter the the small, low altitude drones, I argue for similarly small drones to be used. To counter a drone that costs $500-$5000 to make, one should build drones that cost $1000-$10000 (possibly a bit more expensive when adjusting for R&D and military inefficiency). These will not carry more advanced sensors than what you see on a modern car, primarily a few optical cameras.
Since one can built A LOT of such small drones (10s or 100s of thousand, if needed), they can be spread out along a frontline. They would be carried in a manner similar to switchblade drones or mounted on vehicles, and take off when a threat is detected in the vicinity. A drone (or a small swarm) would search for the enemy drone using primarily optical (including IR), and try to shoot it down WW1/WW2 style.
And, like manned fighters, they would not be restricted to purely defensive missions. These drones could also double as recon craft, do strafing against infantry or even carry small grenades or bombs.
Since these would be recoverable, it would be fine to use a $10000 drone to shoot down a $500 drone, instead of using a stinger missile.
Larger drones would be available in smaller numbers, but those would primarily be used vs larger drones and manned aircraft.
Optical and IR sensors are not adequate for the stated mission. The prices you stated are completely disconnected from reality. You're just making things up.
A Switchblade 300 costs $6000. Swap out the payload with a small gun as well as a better computer (to enable better AI).
Maybe make the wings a bit wider, to improve manouverability. The price should still be below $10000.
Provide one such unit per 20 infantrymen + a couple of units per artillery squad and other units that are particularily vulnerable, logistic vehicles, etc.
