Over the internet with no pstn etc in between could always be free,
Now as far as PSTN lcr has been around forever. Maybe not for home use but I am sure Ma Bell even though back when had tons of cash was always looking for cheapest cost.
Plus once any provider reaches a certain threshold finding lcr with x reliability becomes a cost savings.
So do you mean this a service for end small customers to find a cheap company to use or what happens behind the scenes with any large provider or even a large business using hundreds of thousands of minutes or more?
Plus how up to date are the costs? Real time or charts updated whenever. Do you just need a chart or do you need a asterisk etc. setup making the decision based on real time.
A few different ways to answer the question here. Especially if say homework.