Yes, those starter kits are great, but the real value in LEGO® SERIOUS PLAY® is the methodology.
As a trained facilitator in LSP methods and materials, I’ve seen the power of this methodology at work. It taps into emotion and gets people thinking with their hands, using more parts of their brains than they would just sitting around talking and writing.
The LSP kits are great because of the “curated” mix of LEGO® bricks they contain, specially chosen to help people build metaphors.
(And actually, if you were to assemble your own set of the same bricks “a la carte” it would be much more expensive, so though they cost a pretty penny, they’re actually a good deal.)
https://en.wikipedia.org/wiki/Lego_Serious_Play