Right- in which case they get HW3 for free once they pay for FSD.
Thus my original question remains- why would anyone pay to add HW3 without getting FSD?
Elon Musk is one of them.
Since he explicitly said HW3 was only needed for FSD, and was not needed for anything else (including EAP)
I mean- maybe he's lying- but he probably has more info than we do.
I think you're confused a bit.
When AP2 came out, FSD was an option for $3K. Think of it as pre-paying for a feature that will eventually arrive in the future. So you were pre-paying a cheap price for something that may arrive in about 2 to 5 years.
Elon then future out that he needs a smaller upgrade to AP2, so it was now AP2.5. Again you were prepaying $3K for it.
Remember, there was no FSD at this point. He will still working on EAP, so by if you had EAP or had pre-paid for FSD, you saw no difference.
Fast Forward to today. Elon has already removed FSD from the web site for new vehicles being configured (it's not even an off menu options any more). the price of FSD has already increase to $5K for those who see it on their My Tesla site. Again there is no functionality right now for FSD, but it's coming soon (possibly within 12 months). And by functionality what Tesla means, is the 1st feature set of FSD..
So what this does mean.
If you have purchase it already, then when it arrives you will also get the AP3 computer upgrade for free. When that happens, we have to presume that the 1st feature of the FSD features will arrive with that hardware upgrade.
For those who have not purchase it yet, you have two options
(1) Do nothing, which means you won't get any of the FSD features, period.
(2) Purchase it at whatever price you see on My Tesla for existing owners, or spec out a new Tesla with FSD. Many speculate that it will be $$$ because you're no longer pre-ordering it at a discount, but you're purchasing it now that it's 1st feature is available of the FSD feature-set.
So, to your original question of "why would anyone pay to add HW3
without getting FSD".
People like me paid the $3K for our FSD when we bought our vehicle because it is the pre-order price which will be much cheaper than when it arrives. You could have said that I could have taken that $3K invested it somewhere, and made 25% or more, and then paid the full price for FSD when Elon release it (maybe around $7K or $10K). I choose to NOT to do that. Paying it up front was better for me.
Regardless when someone purchases FSD (either pre-order it way in advance, or when it becomes available), you'll get the AP3 hardware.
It's very simple. Don't over think it. If you have it, great. If you don't, then you have the option to pay more to get it. Either way when you get it, you get the AP3 hardware.