Earlier quoted context omitted.
If you can afford 12 payments with interest, you can by definition also afford to save for 12 months and then buy the camera. BNPL and credit card companies are masters of exploiting psychology and especially currently prevailing wusiness and entitlement ("But I want it now!!!1!", "I deserve to treat myself like a king").
Or you can afford the camera outright, right now. What's better out of these options: 1) Buy for cash the camera now. You don't have any cash in hand afterwards, and the camera is depreciating in value immediately as an asset only offset by whatever you do with it. 2) Buy via BNPL with no interest for 12 months, and pay exactly a 12th a month. You have the camera, but you also have 91% of your cash in the bank that /…
Having my funds reduced to 91% the rest of the year is waaay worse for me, than having it reduced to ~0% the rest of the month. Because, the rest of that month, I'll be super-vigilant, I'll be acutely aware of why I have less money than normally, I know not to make anymore purchases, I know that this month is not for an extra treat, because I bought the other thing. Next month I'll be back up to 100% capacity.
This affects my model of my financial situation, because, it's a camera then.. ~91%, it's a new toaster there ~86% and then ~40% and ~20% and now I get into the dangerous "poor" mindset, it's well proven (and I can personally attest to this being a very real effect) that having less money makes it harder to be financially vigilant, there's opportunity cost* for once, but there's also a tendency to "treat" oneself more because things feel tight, there's a tendency to short-sighted savings (the more expensive pr roll toilet paper, versus the cheaper bulk option that has higher up-front cost for instance).
Now, to begin with, I'd go into "savings" mode a month before buying something expensive, so that I'm not at ~0% for a month, I'd never do that.
* Sure, there could be 100% opportunity cost right after paying in full for something, but the recovery to full capacity is also quicker. I really prefer the large, immediate consequences over the smoothed-out slow-squeeze.