Size ?
Accuracy ?
Mass ?
Cost range ?

There are no cheap, good, mills or routers.
Or lathes.
Everything is a compromise.
Good is relative and cheap is relative.

A chicom cast-iron bed router is probably the best base around 6-10k for 0.5-1 x 1m or so.
Add approx 3k for auto tool changer.

If someone had good routers for milling alu at a cheap price, they would be selling them like gangbusters.

A hobby converted bridgeport or similar would probably be the best cheapest route to quality alu milling, fast, in the 3-5k range.