Persian Archers Question

[Brave Brave Sir Robin]

Ok so I'm playing through a Seleucid campaign and as such, have become quite fond of my Persian Archer Spearmen as well as the base Persian Archers. I have a question about their recruitment however. Persian Archers require the first regional MIC to recruit which is understandable given that they are a basic, if strong archer unit. Persian Archer Speramen require the second, again understandable as they are an archer unit capable in melee. However, their price is cheaper than that of the standard Persian Archers.

Can anyone give me an explanation as to why? AFAIK they have the same or very similar range and the same amount of ammo. The only advantage I can see is that Persian Archers have the fast trait. Of course I'm not complaining, as the spearmen are much more useful in my campaign, especially against those annoying Pahlava and Saka generals.

Anything I'm missing about the regular archers?