Not only did they get the size of the space probes down, they got the transport costs down. They approached spaceX to build a reusable space rocket. SpaceX built the falcon space rockets, they go up to space, then the rocket parts land safely on docking stations to be reused again. NASA wisely approached private companies to make space vehicles so they can get the cost down.
The pandora space probe is smaller than a person but it is capable of looking at stars when their planets transit between us and them and working out what light rays are from the planet's atmosphere and what parts are from the star. The point of pandora is to help make decisions for the James Webb space telescope because it is so busy, it is hard to decide what places to look into and what areas to neglect. If the chemicals in the planets atmosphere are interesting, they will get the very busy James Webb telescope to take a closer look.
The two smaller cube satellites are Blackcat and sparks, they will look at black holes and also study solar flares of low mass stars.
