It's hard to directly compare the challenges of growing fungus vs. meat. Remember that in the case of fungi, the desired product for the food industry is usually a specialized reproductive structure (mushroom, truffle, etc.), produced by the fungus only occasionally, and according to complex environmental cues. So you need a more or less complicated fruiting protocol, depending on the species, on top of maintaining the fungus in culture. This is quite unlike meat, where you are "just" trying to grow a complex of somatic tissue types that is present by default in the wild organism.

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.

Truffles are like wine. The taste isn't the product. The product is the backstory, the where and how of the production. Those paying top dollar want their food to have a biography of picturesque farms tended by hearty farm folk, with a few inoffensive Labradors throw in. The boots and pants can be muddy, that shows that they are close to the earth. But never the shirts. No self-respecting farmer would dare be seen in a dirty shirt.

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.

Well personally I'm near obsessed with truffles and for me it's all about the taste. It's such a unique and complex taste and I think that's the real product.