I’ve been trying to seek clarity on the situation with domestic fares since Ethiopian Airlines announced a 40% reduction in May (see http://www.newbusinessethiopia.com/index.php/en/market/106-travel-tips/799-ethiopian-airlines-cut-domestic-flights-rate-40)
So far as I can ascertain it, the full fare for most domestic flights, for instance booked through the website, remains about the same as it was before, typically around US$130 per leg.
However, it seems this fare has been vastly reduced (by more than 50%) to passengers who have booked their international flight to Addis Ababa with Ethiopia Airlines. In this case, the fare is typically around US$55-60 per leg!
So far as I understand it, to take advantage of this massive discount, you must first book, pay and be ticketed fir your international flights. With that ticket number, you or any operator can then book the domestic flights at any Ethiopian Airlines ticket office.
Of course, what happens in theory and in practice aren’t always quite the same thing, so feedback from anybody who tries this would be much appreciated!