Stockopedia explains P/S...
Some argue that, since sales figures are less easy to manipulate than either earnings or book value, the price-to-sales ratio is a more reliable indicator of company value.
When EPS are negative or depressed temporarily the Price to Sales ratio can be a more useful indicator than the PE Ratio, and a low P/S can indicate a higher profit potential if the stock recovers. Some commentators have called it 'The King of the Value Factors' and look for P/S ratios of significantly less than 1.
It should be noted that the P/S ratio was abused during the dot com years to promote companies with no earnings or profits.