A factor I don't see mentioned that I think is relevant: Repricers

Google "FBA repricer" and you'll find companies like https://goaura.com/ and https://sellersnap.io/.

These are a must for any mid-size seller. Their goal is to pretty self-explanatory; reprice your ASIN, live, to hit maximum sales. If your competitor is selling the same mug for $10.00, the repricer sees that and immediately reprices your mug for $9.99.

Its one of those "Well, if I don't use one, others will" situations.