I think this might be a cultural mismatch. Expert witnesses in the UK can be paid, but the sums involved are pocket money by American standards. Legal proceedings there also tend not to run as long, notwithstanding the Bleak House stereotypes.
Knew one, who got tired of his fee being swallowed by his employer and shifted to a smaller fee, and a very large in-kind: his choice of Michelin starred restaurant, his choice of wines. No questions to cost entertained. Everyone wound up happy I guess.
That’s only the scale that Legal Aid pays. It doesn’t bind anyone else, including the CPS.
Experts are otherwise free to charge whatever fee they like on a commercial basis, though in civil matters, the more outrageous the fee, the smaller the chance that it would be recoverable from the other side if costs are awarded.
https://www.gov.uk/guidance/expert-witnesses-in-legal-aid-ca...