If "true free market" also includes free from control by corporations then, yes productivity increases and competition will lead to lower, real prices. Even without anti-trust intervention though it seems like monopolies don't last. So we'd just need to look at a larger timespan.

One carveout would be prices of services that don't experience competitive productivity increases. Examples would be education and healthcare. Those prices go up due to Baumol Cost Disease (which is commonly made worse by governments subsidizing demand). If we look at the market as a whole though prices still go down, otherwise AFAIL Baumol wouldn't happen.