Amazon USA's pricing strategies

Interesting observation made regarding "shipped from and sold by amazon.com" products pricing strategy carried out by Amazon.com. Amazon often maintains itself as the lowest price for a product it sells, but in many cases it will keep its prices consistently higher than their competition, yet retain the buy box. Now the interesting results come here: Above a certain price point, Amazon wins all the sales from the buy box (no surprise, since they retain the buy box), but go low enough, and suddenly Amazon loses sales to their competition, despite Amazon's retention of the buy box. This can not be explained by the actual price of multiple units adding up to the key $25 level. So far, an explanation for this is unknown.