SP cost confusion.

As I was looking into skills with high SP cost for arena scoring I noticed on both here (the gamepress site) and gamepedia it shows the breaker skills (axebreaker, lancebreaker, R tomebreaker, etc.) costing 200 SP for the 3rd level of the skill. I see on the units that give the breaker skills like Eliwood, or Abel they cost only 200 for the 3rd level. But when I look at my Sanaki for example who inherited axebreaker it costs 300 SP to learn the 3rd level of the skill. What am I missing here? What is the reason? does this affect arena scoring since it's a 300 Sp skill on this character?