I think some people will be fed up with the pit shop seems you have to do a lot of (grinding).
I earn around 20/40 wumpa coins each race (not sure why I sometimes earn 20 or 40). (Oh yeah online doesn't seem to pay out more).
That's on average 30 wumpa coins.
The pitshop seems to change daily and gives 8 things.
Example:
Summer time : Character/Colour/skin and another skin for 7200 wumpa coins.
Doom buggy kart: Well a kart for 4200 wumpa coins
Nash: A character for 1500 Wcoins
And 5 other seperated stickers/colours/skins all around 1000-2500.
So if I want to unlock a character I have to win around 50 races/challenges etc...
If I want to unlock everything today I need +21.000 wumpa coins that's around 700 races/challenges won. You can do atleast 10 races/challenges a hour, so I need to play 70 hours today to unlock everything!! OH well wish me good luck!!
