While lab-grown cell cultures can be a solution for making fake meat for rich vegans, it is unlikely to ever become an efficient protein production method.
There already exists an alternative protein production method, the use of a genetically-modified strain of some fungus (currently there exist such strains of the fungus Trichoderma), which has been modified to produce a soluble protein with optimal amino-acid profile, i.e. either whey protein or chicken egg white protein. This method can produce protein powders at a low cost, with the potential to become cheaper than the same proteins from milk or eggs.
I have experimented for a few years with using only vegetable protein sources, but I have eventually given up, because the restrictions that this imposed on my meal choices were not worthwhile.
Now, I use besides vegetable protein sources also some whey protein concentrate powder (which not only has a better composition, but it is also much cheaper than any industrially-produced plant protein extract, having about the same price as chicken meat). Thus I can cook whatever vegetable food I want without worrying about the protein content or the amino-acid profile. When necessary, I mix protein powder in the food that I am cooking, to ensure an adequate protein intake.
This is good enough for me, because even if I enjoyed eating various kinds of meat in the past I feel no need now to eat fake meat.
Here on HN there was last year some news about a startup attempting to produce proteins in this way, by fungal cultures, but at least for now they had in mind only industrial customers. Nevertheless, if in the future such cheap fungus-produced protein powders became available at retail, that would solve for me, and for others who might not care about expensive fake meat, the problem of the protein content of a vegan diet.