A quick search would lead to several recent threads on this very topic.
Basically, there are too many variables to say what your costs would be. It depends on the boat, the tastes of the crew in terms of lifestyle and food, cruising region, your skills and self-sufficiency level.
if you stay on the hook and eat simple, low cost foods on a small, easily maintained boat, your budget will look one way. If you stay in marinas, on a large boat with complicated systems and eat at restaurants every other night, your budget will need to be considerably larger.
If you have a fairly self-sufficient boat and are able to do most of the maintenance on it yourself, your cruising costs will be far lower than if you need to constantly go into the marina to re-charge your batteries and replenish your water supplies, and have them do the basic maintenance on the boat.
Your boat's size will often influence costs. The larger the boat, the more expensive it is to maintain, haul, repair
, dock, etc. A 40' boat will cost two-to-three times as much to maintain as a 30' boat. It is also almost 135% larger than a 30' boat, not the 33%, since it is larger in length, depth and width.
The way your boat is setup will often influence costs. Do you have enough of a battery bank and passive charging capacity to not have to run the engine or use shore power to recharge your battery banks? Electricity costs money--either in passive charging systems, fuel
or dock rental. Same with water. A boat with solar panels, a wind generator and a watermaker can avoid using marinas for a long, long time.
Beth Leonard's book, The Voyager's Handbook, has some costs for three different types of boats, a very basic cruising couple with small boat and modest needs, a medium level for a family of four, and a burn-through-money-like-water budget. However, the book's examples won't take into account the price increases caused by the extremely high fuel
costs over the last two years. The cost of diesel and gasoline has basically doubled in many areas, and the costs of transporting all goods has been affected, causing increases in the price of food, manufactured items, etc.