Me too. The Treasury begs to differ.
Initial Naval Training is 10 weeks & it costs more than £7000 to get a recruit to Raleigh, after which it's about £1000 a week to train each RN recruit (nearer £2k for RM), including paying them a wage before they can do their job.
The shortest training period for any RN branch is 3 months (for qualified nurses joining with a Nursing Degree). After that, the shortest training pipelines are NA(AH), STD & Supply Chain who each take 7 months to train, prior to on job training/task book training.
Whatever branch you join, you've cost the taxpayer somewhere between £37,000 (jobs above) and £167,000 (student nurse) to train.