Nah, that's completely arse about face fella, Will is correct in principle.
There's a huge flaw in your argument here: if you're having to buy the raw materials AFTER an order is placed as you don't have it in stock, THEN the price would be higher as it's reflective of what you're having to outlay. If, however, you already own the materials, then you price it to make a profit on that price that you bought the materials for whenever it/they were purchased, and subsequently (unless you're a bit of a scammer/chancer and hoping the customer is a mug) it will possibly/probably be lower, if nothing else to make it an attractive quote.
One question which sprung to mind immediately based on your model of how commerce works...
If a company is concerned with a new price increase, and charges the higher price they will soon be using on old stock simply to compensate for their prospective new repurchasing price ... how did they ever get the materials in the first place? At some point, that company took a hit to get stock in the warehouse, etc. in the first place otherwise they'd have nothing to sell!
Just to reiterate, this is OLD STOCK, CURRENTLY PAID FOR AND OWNED we are all talking about here, not a hand to mouth business where a company gives a quote for something they don't currently own.... that would be bonkers as they buy it at point of quote, which is whatever the current market value at that second is.
Ironically, I literally had this exact same 'argument' this morning when buying cartridges, pre price increase. Shop owner (always been a bellend) said he'd heard a price increase was imminent but nothing concrete. Asked if I came in next week if I could have them at today's rate, just to play safe as he had thousands in stock. He said no problem. Called Gamebore, out of curiousity who said price rise is from March 8th. Called the shop back to let him know, out of courtesy and that it would affect him, trying to help him out... his response was to say that I'd better get in before the price rise as he'll put them up! So basically, he's a greedy f**ker who wasn't going to honour a conversation less than 5 minutes previous after I'd gone out my way to let him know something that would affect him. I said this to him and he grudgingly said he'd do the decent thing, but still left a sour taste in my mouth. Great customer service right there.
As it turns out, I could make it this morning, so after a moral wrangling with whether I wanted to even give him my business and money, I got 1000 Velocity along with the satisfaction that he's going to put the prices up come Monday for nothing more than pure profit and I've taken a tiny chunk of that off him!
Needless to say I'll be going to William Evans from now on instead.
So, in essence, nobody is selling at a loss if the products you CURRENTLY OWN were purchased for less than what you're selling them for, especially if the margins are the same regardless of price increases. I'm sure Will can walk anyone through that again if needs be, it's a tricky concept.