What the putting off costs
I've left the costs until now because you know the main one already. If the thing is serious, delay can make it worse, and chapter 5 said so once. This chapter is about the costs you pay even when the thing turns out to be nothing, which is most of the time. They're easy to overlook because none of them arrives as a bill.
What follows is my own account, and I offer it as observation.
You pay in dread first of all. Chapter 1 described it. The thought comes back every week or two, and at ten past three it comes with force. Each visit is unpleasant and none of them settles anything. If the mole is harmless, which it probably is, then every one of those bad quarter-hours was unnecessary. A ten-minute appointment in March would have prevented six months of them. You've suffered many times the discomfort of the appointment, in instalments, in order to avoid it.
Here the habit has the shape this series keeps finding. I don't want to press the comparison with a drug, because nothing is being craved. But look at the sequence. The thought arrives and produces discomfort. You push it away with "it's probably nothing", and relief follows. The relief rewards the pushing away, so you do it again next time. Meanwhile the underlying discomfort grows, because the longer you've left it the more there is to be afraid of. The habit relieves, moment by moment, a dread that it's building up over months.
Then there's the checking. Many people who won't see a doctor examine the thing themselves, often. You twist in the mirror to look at the mole, or press the lump to see if it's changed, or search the internet at midnight and read the worst case. This gives you the anxiety of medical attention with none of the benefit. You aren't qualified to assess it, you have nothing to compare it with, and the internet can't see your shoulder.
You also lose a baseline. If you'd gone in March, there'd be a note on your record, perhaps a photograph and a measurement. If the mole changed later, there'd be something to compare it with. As it is, you stand at the mirror in September unable to say whether it's bigger than it was, because nobody recorded what it was.
The work grows, too. This is clearest with teeth, as chapter 7 described. A small cavity becomes a large one, and a large one becomes an infection. The treatment gets longer, more uncomfortable and more expensive at each step. Most adults in England pay towards NHS dental treatment, and the more complex the work, the higher the charge.
Shame accumulates. After six months you're no longer only someone with a mole. You're someone who has ignored a mole for six months. You start to imagine the doctor asking, "And how long has it been like this?" So there's a second thing to avoid, which is the admission that you've been avoiding. People stay away from dentists for years longer than they otherwise would, purely from dread of being told off. For what it's worth, clinicians see delay constantly and rarely comment on it. A simple "I've left this longer than I should have" covers it.
And the people around you may be carrying it too. If your partner knows about the mole, they've probably mentioned it more than once, and been put off more than once. They worry, and they can't make the call for you.
Against all of that, the putting off gives you the safe feeling. Chapter 3 showed that the feeling corresponds to nothing in your body. You pay for it in sleep and peace of mind, and sometimes in teeth, and very occasionally in much more than that.