£250k's not bad for a high-tech prototype of any kind. Theoretically, mass-produced lab meat should work out cheaper than field-grown - a cow takes 2-3 years to mature, during which it needs to be fed and cared for, requiring lots of land, heavy equipment, labour, vets' bills, etc. I don't know much about the final stage of the beef-making process but I'd assume it's quite labour-intensive, too.
So you'd think that a production line akin to that of a pharmaceutical company would work out quite a bit cheaper in the long run.