A strategy to pay the local fare on minibuses between cities
TL;DR
Don't ask drivers for fares upfront: They'll coordinate with each other to quote an inflated price.
Pay on board: Mid-ride (50–75% through), a fellow passenger acts as the fare collector to combine payments for the driver, giving you a better chance at local rates on less touristy routes.
Travel in stages: Skipping the direct desert road lets you ride along the Nile with locals, visit Kom Ombo, Edfu, and Esna, and reach Luxor
Kom Ombo transit tip: It has North and South bus stations connected by a separate local minibus.
When traveling between cities like Aswan and Luxor, don't ask the driver for the price before getting on. They'll often just quote a hugely inflated rate since you don't know what it should cost.
Once you're on board, the collection process is quite unique. 50-75% of the way before the destination, a passenger will act as fare collector and begin collecting fares from everyone, providing change and then handing one lump sum to the driver.
For a memorable experience and potential savings, consider taking the trip in stages instead of the fast desert road. You'll get to travel with locals along the Nile and can stop to visit temples like Kom Ombo, Edfu, and Esna along the way, often for only a quarter of the cost of an inflated direct ticket.
It seems on the shorter, less touristy routes you have a better chance of paying the local price. In my case I visited Edfu and Esna and got into Luxor on the west bank before sunset.
One thing to note, for Kom Ombo there's a North and South bus station, a separate local minibus goes between the two