Speaking of two jpop divas:
Seiko Matsuda 2015 best sold 150k, and her last hit was on 1995. Her studio albums nowadays use to sell 15k.
Akina Nakamori 2014 bests sold 80k each, and her last hit was on the 80s lol. Her last two studio albums sold 10k each.
ayumi's career is way more healthy than those two, I don't see why she can't have great sales with a best album. (something like 100k). Honestly it makes me a little bit mad
they are losing a great opportunity being this her anniversary year.