Basalt is about 2.5 times more expensive than plain steel and about 1/4 the cost of stainless steel. We use all three plus polyfiber in our construction depending on the engineering needs and exposures.
Plain steel is strong and cheap but can corrode. We used this in areas that are well protected and thick concrete. See:
http://sugarmtnfarm.com/2013/11/18/interlocking-pours/
Stainless steel is strong and expensive and won't corrode. We used this in critical areas such as the overhead truss beam that supports the high rail that may get as much as 30 tons of force dynamically. See:
http://www.google.com/search?q=site:sugarmtnfarm.com+stainless%20steel%20rebar
Basalt is between the two on cost and strength as well as testing and also will not corrode. We used this in thin areas that are prone to acid, bleach and other corrosive exposures. e.g., partition panels, thin arched ceilings, brine room (high salt), etc. The basalt does not have as long a track record so I'm not depending on it in critical area like the overhead beam where the stainless steel is the primary reinforcement. See:
http://www.google.com/search?q=site:sugarmtnfarm.com+basalt
We also used polyfiber in all the mixes and we'll be using basalt fibers in the mixes where there is higher heat levels such as around the smokehouse and ovens. See:
http://sugarmtnfarm.com/2011/11/07/good-pour-great-pour/
Each reinforcement has it's pros and cons. Mixing them works well.