Neither good nor bad, but indicative of a character who has just started out.
As you level up your mercantile, the price you buy for will gradually decrease and the price you sell for will gradually increase. (Right now, you max out at 110/90.)
Ah, I see. Seems a little strange to me, but it does make sense (thinking game logic anyways). Either way, I'm looking forward to this game and this minigame\system.