The buy box is a mystery, whoever says they fully understand it is lying. One fact us the FBA gets it for a much higher percentage than fbm even if the price us quite a bit higher. Some of my FBA prices are quite a bit higher than my fbm prices due to the new huge volumetric fees charged by FBA.
If you want to go fbm, have it as competitive as you can and the best customer service and odr and you will get a few sales.
Yes, you are right but what i feel it varies from product to product. But the thing which is game changer is your handling time, I suggest if you can handle shipping time of a day then percentage of winning buybox is higher.
The FBM price is usually low because buyers have to pay for shipping charges. In contrast, the FBA selling price includes shipping charges as well. Buyers usually prefer FBA because of the fast shipping by Amazon and the easy return policy. You can list as FBA for more sales, but profit margins will be affected if you go with low prices.