I recently contacted adwords support via email about a competitor using this term and what the policy is on this. They responded by stating this is acceptable and don't see a problem with their ad. I thought the ad was deceptive since half the other ads offered lower pricing but I can see how using the ad copy "lowest prices" may increase his click thru ratio in this weak economy regardless of being true or not.
It is common to see "low prices" in ad copy but I don't see ads that state "lowest prices". Is this more common now? Are ads getting approved for using "lowest prices" without 3rd party support?
It may help you get a high CTR, but once people get to a site and see they aren't in the fact the "lowest prices" they will most likely leave to find the real lowest price. Again, back to CTR not being the most important metric.
"low price" is OK. Your price can be low but you cannot make the claim, which you can't substantiate, that you are indeed the lowest. Or the best, the cheapest or the biggest.