Ending prices with 99 is manipulative. We accept it from businesses because we’re conditioned to, they’re businesses after all! Being manipulated by businesses is just how society operates, part of the environment we live in. But if an individual offers us something for a price ending in 99, we’re much more likely to be suspicious of it.

The article actually explicitly mentions this, and suggests you list things for 25 under instead of 1 under, for example, as it won’t immediately trigger recognition that you’re doing this.