Latest exchange rate has GBP 1.00 = 1.37 USD
So that 250,000 GBP to fill their bunkers is really only 342,500 USD. Not far off your figure.
Costs them a pile to fill up, but they don’t have to do it very often.
And fuel burn is mostly a function of hull design, props and speed. A megayacht optimized for speed, to get over 30knots, will burn several times more fuel per mile than one optimized for range that moves at ten knots with a max of 15.
My last two novels dive into megayachts and small warships extensively. In fact, the plot of my last novel involves an old steel trading schooner salvaging 96 barrels of diesel from an abandoned NATO base in Greenland, for resale in Ireland, post economic collapse.
If you want to talk about trading schooners, megayachts with bling, "research vessels" that are really low-profile megayachts and even small private warships, I'm the guy.
