Your dealing policy with your suppliers is business-to-business, I agree with it 100% and it is admirable. That is right and proper and as it should be. But this is an instance of an advertised price to the general public, a purchase made by a frequent customer or a one-time-only buyer doesn't matter. The selling price listed is the seller's responsibility, not the customer's. That is also proper and as it should be.
Would you ever call me and say "Hey Brad, you know that Super Turbine Booster Fooster you bought from us last week? Well, we goofed on the price..."
No, your high integrity and business reputation wouldn't allow for that. That is the only good response too, except of course addressing the cause of the problem in your company internally.
case the OP's conscience can rest easy and sleep well, and if that vendor refuses to ever sell to him again that would be their fourth
First off, my response here is of no inference or reflection on the original post. Now, I'm just delving into my own feelings..
Over the years, I've seen plenty of social-media posts where car dealerships mucked-up and listed (for instance) "New 2017 F150, now only $3,995!!" in a newspaper ad, or website listing..
Now... You know damn well that's a mistake. You know somebody dropped a zero, or something. And you know that if you pursue that price, you're looking to gain at the expense of another's error.
A supercharger listed at 99.5% less than other competitors' list-prices? Come on now...
And I do not see any difference in what basic ethics/principals should be business-business, or business-customer. Or citizen-government. Or stranger-relative.
Just recently we mistakenly had a $380 a/c condensor listed at $10 online, and within a matter of hours 7 orders slid in... Seven people trying to dive on a $10 condensor, and I'm sure they knew it was an egregious error. We caught the mistake before anything shipped out the door, so unwinding the problem wasn't too difficult, and each of the 7 customers were understanding, friendly, and sheepishly admitted "yeah, knew it was too good to be true!". So it worked out well.
Don't know what I'd do if one of the seven had made a stink of it, because luckily, every time we've had one of these types of screwups, our customers (bless them) have always been top-notch and understanding.
I don't have one set of standards for businesses, another for customers, and another for family/friends. I just have standards, and I try to abide by them, although we've all been guilty of falling short in the past. We all live in glass houses.