Funny enough, I did this with Postmates once.

I ordered a meal which Postmates estimated to be ~$16. When they finally billed me it was charged at $32.

When I contacted them they told me that the prices reflected aren't always accurate, but I'd say a price going up double is a bit of a goof on their part. They were unwilling to refund the payment, and so I called my bank and explained the situation. The bank associate on the phone took care of the charge back as a measure against them.

After that, I've never ordered from postmates again. I get that prices can vary, I'd forgive it to a certain degree. But double the price? Nope.