The U.S. Navy is testing a new light missile called the Griffin that weighs about 33 pounds. This is roughly comparable to Viper Strike air to ground missiles, a howitzer or mortar round, or a heavy tank round. But, it is lighter than a Hellfire missile used by an Apache attack helicopter or armed drones, a "smart bomb" dropped by a jet fighter, or a typical round from a warship's naval guns. And, it is heavier than, for example a grenade launcher or armor piercing round from a heavy machine gun or round in the canon of an A-10 Warthog ground attack aircraft.
The system has done well in recent rounds of naval testing and is already in use on C-130 cargo planes modified to serve as gunships for the Marine Corps against similar targets so it is more than vaporware. It is also used on a variety of armed drone aircraft (fixed and rotary wing), military helicopters, and A-29 Super Tucano ground attack aircraft. Apparently, it can be retrofitted to be mounted on existing vehicles such as reasonably large aircraft and ships, fairly easily. One can imagine mounting them on docks or buildings that need to be defended, Abrahms or Bradley sized armored vehicles, a Humvee or coastal patrol boats of the size class used by the Coast Guard as well.
In naval applications, the plan is to use the Griffin missile to destroy fast moving small craft of the kinds used by pirates and as gunboats in Iran's navy, at ranges of about two kilometers or less (the maximum range is about 5.5 kilometers, quite a bit less than even the smallest of naval guns on U.S. warships or howitzers). It is being considered for missions including deployment on the navy's new Littoral Combat ships. Reduced collateral damage is also attractive for these kinds of targets, which may be near their civilian or military targets when then are hit.
A lack of appropriate weapons systems to deal with this kind of threat effectively, nimbly and without the overkill that would allow an opponent to win a with a war of attrition or swarm strategy has been an important deficit in U.S. naval resources that has been identified in training exercises and a handful of real naval engagements in recent years. This system, which does not seem not terribly technologically ambitious compared to existing naval weapons systems, seems to fill that gap in capabilities reasonably well.
Presumably these kinds of weapons systems can be procured for an affordable price (although the source doesn't quote a proposed price for either the launcher or the missiles, usually missiles cost more than dumb artillery rounds), relative to the status quo. This source says that a guided Griffin Missile B costs about $45,000 each - less than similar but heavier missiles (the slightly heavier Javelin missile reputedly costs about $75,000 each and the much larger RAM missiles cost about $450,000 each) and fairly comparable to the cost of a guided artillery round for a howitzer (Excaliber). The launchers apparently cost something on the order of the single digit or low double digit millions of dollars, although I haven't seen very specific numbers.
Most of the serious threats to the U.S. Navy, such as attack submarines, advanced fighter aircraft, stealth drones, and cruise missiles are at least confined largely to "high end" naval threats that few plausible hostile countries have available to them, even if they are not strictly restricted to "near peer" opponents. A diesel-electric attack submarine can easily cost $100 million. Figher aircraft cost tens of millions of dollars. Each drone and cruise missile can cost several million dollars.
In contrast, explosive filled speed boats and pirate craft are much more easily available, so this gap in the U.S. Navy's countermeasures resources has been particular troubling. One can buy one, outfitted with weapons serious enough to be a military threat for hundreds of thousands of dollars. Any naval threat that private individuals in Somolia can afford is effectively available to anyone interested in taking on the U.S. military, and in asymmetric warfare like that, winning inefficiently can be almost as bad as losing - the opponent may not be able to kill you, but they can force you to spend far more money on the conflict than they do indefinitely while waiting for you to go away. (Of course, one can only be so efficient in asymmetric warfare when you ships that you mount the missiles upon cost half a billion to a billion dollars each, regardless of the efficiency of its weapon systems.)
There is reason to question, however, how important the niche of short range ship based anti-small craft missiles really should be with an appropriate strategy. No ship with short range missiles can match the ability of small aircraft to outrun anything on the water or to take on opponents on land in coastal areas. It could be that the only ships that end up using Griffin missiles are those that weren't smart enough to deploy helicopter gunships to address the threat first. But, if the cost isn't overwhelming relative to the entire ship, a belts and suspenders approach to one of the most common types of potential threats makes sense.