On top of this, truffles have complex ecological requirements (mutualisms with plants and associations with soil microbiota), so unlike saprophytic species they are very difficult to grow in artificial culture to start with (even just spore germination is tricky). Fruiting is tied to seasonal changes in the host plant and we're only just beginning to understand the genetics underlying all of this.
I agree with you actually, but I think it is some decades away and will require lots of GM, and lots of work on how to get control over metabolic and fruiting systems without changing flavor profiles.
This is fashion food. They will pay extra for the lab-grown stuff once fashion shifts back away from the dirt and towards 'clean' synthetics.