Corporate America is discovering that artificial intelligence may be revolutionary, but it is also noting that it is not cheap and as a result is beginning to ration access to its employees in an effort to cut costs.After more than a year of urging workers to use AI for everything from coding to research to routine office tasks, some of the country's biggest companies are beginning to ration access, track usage more aggressively, and steer employees toward cheaper tools as costs rise faster than expected.The pressure point is the token, the basic unit used to measure AI computing. Every prompt…