I agree with this, but...
If a person figures all of that out, and no components are around, they still go ahead and order the parts needed for the build. If the parts arrive and still no components, no worries, the build still has to be completed and that takes time, too. If the build completes, and STILL no components....paper weight.
I lucked out- I have a switch barrel being built currently. I ordered all of the parts last August and got them late November/early December. At the time I ordered the parts for my build, I was able to get brass or already had it. Primers, too, and bullets for one of the barrels. What I did not have were powders for either, or bullets for one of the barrels. I have been VERY lucky in that I was able to find everything earlier this year, though I'm pretty short on one of the powders.
If I had needed primers though, or wasn't able to trade for some things, I'd have been hosed. I think many people are in that boat, especially new reloaders or people who have a couple cartridges they load for but are expanding their horizons- they probably don't have much, if anything, to barter or reuse.
That is why I think it is silly for some folks to take the "failure to plan is planning to fail" attitude here. Nobody plans for the world to be shut down for over a year- even if you had a gut feeling and were able to stock up, you probably burned through quite a bit if you were shooting semi-regularly. Spending tens of thousands of dollars in the off chance that you need to be stocked up for an 8 year shortage is just something that very few people have the capacity to do. I'm not saying you are taking that attitude- I'm saying that a few people on here are, and they probably just need to keep their collective mouths shut because they're only looking to poke some bears.
For that matter, I should probably keep mine shut as well, haha!