User blog comment:Shnopp.shniederheimer/Worth the Donuts? - Most Ideal Decorations/@comment-25021853-20140626180821

I had come to a similar conclusion by doing the math in my head, but I tended to look at it as Donuts per Percent. Two things: 1) I can't remember when the Jet Engine Bike unlocked, I know it was Level 30 or so, and 2) your numbers are correct, but you forgot to multiply by 100 to convert from the raw ratio to Percent (i.e. the Picket Fence is 0.05%, not 0.0005%).