I read a story once about a book on Amazon had an outrageous price due to two competing sellers that each had an algorithm to automatically adjust their prices based on the other. I don't recall the exact logic on it but the first would purposely set their price slightly higher than the second. And then the second would rest their price to slightly lower than the first. But the the percentages used caused both stores to keep rising. eventually the book got up to some insane number.