Operations costs are under the heading of "Readiness." First sentence in that section says this: "The Navy plans to spend $57.7 billion on operations and maintenance in FY 2020."
Reading down through this, your head will swirl with all the numbers. It can get "rather meaningless" as a result. Making it even further "meaningless" would be that this is what the Navy proposed for the previous fiscal period. What Congress then actually gave out is substantially different, and can be found by searching for articles which detail what Congress then did. The most notable example right away offhand is that this is the "infamous" budget which proposed to cut the funding of the USS Truman RCOH, to apply the savings to development of more advanced technology (detailed in the article.) When this got publicized--including with some threads here--there were a lot of upset people, and Congress promptly shot that down. Truman is getting her RCOH! Congress also refused to fund all of the Navy's request for 10 new LUSV unmanned ships. They funded 2, and after much debate, and those 2 will not be armed as the Navy had wanted. The other 8, and whether or not they get armed, are a subject for future budgets/budget debates.
So, I spit out the Flight III build number because it happens to be a figure I know off the top of my head, and it provides a comprehensibe comparative reference for the number.
You are entirely correct that there is often a great amount of publicity given to how much such-and-such a weapon cost to buy, but we basically never hear of how much it costs to operate, and that is actually--over the long term--the biggest cost by far. There are 2 numbers for every weapons system...the purchase price, and the operating price. The former is commonly "front page news." The latter is seldom considered by most. The figures are out there...our government keeps track of everything...but you have to dig more to find it. And, while a published purchase price is usually stated as "the unit cost," operating costs tend to be given--as above--in lump sums. ($1.28 billion for the new frigate. $57.7 billion for "operations and maintenance.")
The whole exercise is a matter of "robbing Peter to pay Paul." We need to stay on the cutting edge of new technologies. We also need to keep the current fleet running. The single best illustration of the problem as a whole is exactly the Truman issue. How much money we would have freed up for use on modernizaton is spelled out in the article. On the other hand, the capability we would have lost in the "here and now" was ultimately deemed unacceptable. However, NOT investing in modernization leads to a fleet with high operating costs, which take even higher operating costs as it ages and needs more maintenance. Current naval leadership is of the general mindset that we should invest money now in a fleet which will be newer, with lower operating costs later. To get there, they advocate trading away older systems currently serving. Congress, and some in the Pentagon disagree, and advocate that we keep what we've got, and even build more of the same. Another good example of this "war of ideas" now going on is the Ticonderoga class cruisers. Many in naval leadership want to let them "expire gracefully" when they hit the end. A contingent in Congress wants them all to be given mid-life upgrades, extending their service. This helps keep present number levels up, but also keeps ships with 300-man crews of high operating costs over the long term. An unmanned vessel, or more frigates using smaller crews, will have much lower long term operating costs. The technology for an unmanned vessel especially is not yet proven, and only time spent actually operating them will generate the needed data. To get that operating data means building operating ships, and that requires eliminating old serving ships because there isn't enough in the budget to do both.
This is "the whole problem" going on right now in a nutshell. These are the arguments being made, in Congress, and in the articles which deal with the future of our fleet.