I expect there is a fixed cost of owning the boat and living on it regardless of whether it’s moving or at a dock. So the cost of travel is the cost of running the boat which is fuel and maintenance. For a boat like that I figure on 1 NMPG fuel burn, so let’s say conservatively $4 per mile. Then perhaps $1-$2 per mile for maintenance? That might be in the high side. So I would say roughly $5 per mile to operate the boat.
For a 60-foot boat, I'd use a guestimate of $150/night when in a marina. May seem high to some, but most countries have added tax in the 12%-20% zone; plus electricity and water are metered. Marinas tend to be seasonal in many areas so the costs are recovered over 5-mos vs 12.
For fuel, would use $1/nm as TT suggests. Plus generator of $1/hour. Best I can tell, US fuel prices are a bit lower than average.
Food/beverage - probably about the same as you currently spend. We eat out a lot more in Mexico because we like to. I'd guess we spend around $1k/mo on food and dining, but we're not careful about it at all.
For regular maintenance, bottom diving of $100/mo; boat wash around $100/mo. Haul-outs are usually less than in the US.
Scheduled mechanical maintenance - total wild card. But around the same as at home assuming you brought adequate spares (impellors, filters, etc.).
Unscheduled maintenance and repairs. An even bigger wild card. Anything beyond AGM batteries is exotic so there won't be skills or parts if you have an LFP/Balmar setup. Or if your refrigeration or air con go out. Hoses and hose clamps are often difficult to source. Finding the right water pump. Sure, maybe you have spares for some but eventually you will have to source a Plan B part at prices that make West Marine seem like a thrift-store bargain.....if you can find it at all. I would double TT's estimate of $1-$2/mile budget and hope there's money left over - I wouldn't be surprised to see $100k for a 30k circumnavigation.
Other expenses such as flying home from time to time (and leaving the boat); agent/customs fees; subscriptions (mobile/internet/weather); DHL Shipping charges; etc. Easily add $1k/mo.
Right now, I figure we're spending about $5k-$6k/mo including some land-based costs (house that's paid for but has taxes/insurance/utilities). So we're probably spending around $5k/mo ($60k/yr) for cruising related costs. Bigger boat and more fuel plus associated moorage costs, I could easily see that approach $100k/year, probably more since we aren't too extravegant.
Hope this helps
Peter