I think indirectly it does. When your launch vehicle costs hundreds of millions of dollars to use once on a scientific mission you try to put as much engineering into the scientific payload to (1) make damn sure it works when you are paying $200 million for a launch and (2) make sure you can do as much science as possible.

With something like Starship I wouldn't be surprised to see SpaceX cheaply provide a starship approaching end of life to a scientific mission. With cheaper and readily available launch opportunities we could see deep space missions that utilize larger amounts of probes manufactured more cheaply that have much less longevity (die after a year of data collecting) but can do a greater amount of science over their shorter lives. Essentially, using a large launch vehicle like starship as a mothership until they get to their destination. Reducing the need for RTGs.

A billion dollars a launch is definitely an obstacle.

Part of the reason why the probes are expensive is the limitations on the size and mass imposed by existing rockets.