I think that in its current state, it would be worth somewhere between $5-10
It has good content that lasts for a bit, but if you had 5 bucks more? Maybe have a multiplayer racing mode, multiple levels, make textures a little more high definition, and maybe add a level creator. all that might actually be more like a $15-20 game
Don't take it only from me though, I usually don't buy games more than $10, so I'm kinda cheap. Get some other people's thoughts, too.
Oh, and sorry for replying so slow, I was playing Rec Room.