It's hard to find a competent robot vacuum cleaner under the $500 threshold, but Prime Day gives us a unique opportunity to grab heavily discounted models. The Eureka J15 Ultra is a surprisingly great option from a company well-established in the vacuum space,

SAVE $500: As of July 8, the Ecovacs Deebot X9 Pro Omni Robot Vacuum is on sale for $1,099.99 at Amazon. That's a 31% savings on the list price.