That’s kinda the point, darling.
So what’s the problem, cutie pie?
Do you really think that is a more likely scenario then the customer hearing the salesman say $420 during the course of their conversation and thinking that is the price?
No problem here, darling. Just sitting back and watching my salient point made for me. The OP is bitching that his customer is confused, and yet the SDMB is also confused.
But the conversation started with them haggling over the “$460 plus tax” price. It seems much more likely to me that the salesman said “$460 tax included” than jumping to “$420 tax included.” If he went from $460 plus tax to $420 tax included, he’s not a terribly good salesman.
One possible scenario, I suppose, is that the salesman said “$420 plus tax, which puts us at about $460 with tax.” That is possible. But the customer, from the sounds of the OP, was talking about paying $420 total, tax included.
There’s nothing confusing except perhaps the telling of the story. The offer was simple: “$460 tax included.” You want to get rid of the case? OK, “$430, tax included.” That’s about as transparent as pricing can get.
Again, that’s kinda the point. If Cosmodan was as confusing in haggling as he is here…
This is what I’m talking about. I think the customer didn’t understand what tax included meant and the salesman had to explain it to him probably exactly like you just said. Then not being the smartest person to begin with went away thinking the price was $420 and was confused a couple of days later.
See, even you’re confused. From the OP:
No. Read it again.
In all fairness, we like to argue and nitpick here - that can sometimes look like confusion. 
I don’t know about you but I don’t need to know nor care about the exact to the cent price I’ll be paying with the tax. No need to bother with decimals, I’d just say “close enough to 10% - that’s $42 - price is going to be about $460 or so”. I don’t need to know that it’s going to be exactly $458.85 and I don’t know why anybody else should care that much either.
Of course, I don’t even care about tax to begin with so I wouldn’t even be bothering to do that much arithmetic.
I’ve had $8 in the bank account before and I still don’t give two shits about tax and have never been surprised or run into trouble. If I want or need an item and it says $1199.00 before tax, I don’t care that the tax is going to be another $130 or so. I have already decided that I am going to have this item at a price point near that, and another hundred bucks isn’t going to stop me. If I can afford to get whatever I’m getting, I can afford any tax that comes with it as well, or I wouldn’t even be thinking of getting it in the first place. Much like when I had $8 in the bank it’s not “Oh, well, I can still afford that donut I want. But WAIT, there’ll be another 7 cents of tax on that 99 cent item! I guess I can still afford it” it’s “I can’t afford a donut because I shouldn’t be spending anything right now. Period.”
And while we’re at it, yes, I think it’s more plausible that $420 was pulled out of the customer’s ass in order to try and force yet another discount on the “Customer is always right” point.
Which part? The part where he says the customer paid for it and left with the item?
Or the part where he came back two days later wanting a partial refund from an amount he’d already forked over.
Read the sentence after the one you quoted where it says:
At that point the customer is just thinking about the $460 deal (or about a way to run another scam) and has not paid anything.
I think the customer probably thought that the initial $460 deal included tax but it didn’t. When the salesman then waived the tax the customer then came up with $420.
How much is that with tax included if I trade in a bench grinder and you keep the box?
Ok… Got it.
No wonder the customer was confused. OP is a confusing person.
Sure. At the end of the day, though, the math, tax rates, etc., are all a red herring. The customer may have misunderstood, or done some weird math in his head to arrive at $420 (as the customer said he understood sales tax being a small business owner), or maybe the salesaman got a calculator out and divided 460 by 1.0925 to get 421.05 and somehow that number stuck in the customer’s head out of context, etc. Or, hell, let’s even say the salesman is outright lying. It doesn’t really matter to me. Today, the deal is $460 out the door. You can take it or leave it. If the deal really was $420 with tax included two days ago then I guess you should have bought it two days ago. There’s no confusion or ambiguity with what the offer on the table is now.
Here’s the original quote in context:
It’s clear that the line about paying $460 and taking the guitar is speculative, assuming the customer decides to take the deal. The OP isn’t worded as clear as is humanly possible but you are going through hoops to misinterpret it. I don’t think your reading of the OP is valid, nor is your criticism.
Read up a couple of posts where I said I understood.