There are no highly rated commercial dishwashers available to buy for under $600. The best non-commercial dishwasher available for under $600 is the Frigidaire 18" Built-In Dishwasher, as measured by reviews on Amazon.com. The Frigidaire dishwasher is priced at $574 and has a four-star rating, as of April 2015.
The best-rated commercial dishwasher on Amazon.com is the Miele Professional Full Console Dishwasher, which is priced at $5,615. It features a five-star rating and has eight wash settings that support specialty loads, such as beer glasses, crystal and china. It also includes an automatic water softener and settings for cold or hot loads, up to 160 F.