I have noticed, that the Shiny Tartagon mount that costs 100 lucky coins is for rale in the ingame shop for just 180 Credits. This might be cheaper than intended, since Arachne mount that costs 200 lucky coins is being sold for 630 credits. Simple math.
Maybe the low price is due to the fact, that this mount has been ingame for quite a while, but in any case, it's a nice chance to get it for those, who haven't bothered collecting lucky coins for it like myself :3
Edit: The speed of these mounts is also different, but for the collection's sake it's still nice, in my opinion.