After giving more thoughts... Yeah, credits certainly have a bad reputation so you might lose some credibility from the user point of view. In addition, if you

After giving more thoughts... Yeah, credits certainly have a bad reputation so you might lose some credibility from the user point of view. In addition, if you have tiers of credits (so you have 3 distinct credits, rather than just replacing euro sign with a credit sign), you lose plenty of flexibility. So yeah, I can see why you rejected this option :)