I've seen a few dealer price lists, there is quite a markup. So this is a real example:
MSRP 2999.99
Dealer Price 1499.99
Never saw the manufacturers cost but it's got to be pretty low, I can't imagine they would let the dealers make all the profits.
There is a commonly used formula, but in practice, it varies quite a bit. I know that a lot of internet direct sellers have small margins. Manufacturing costs are also complicated, as on paper it typically only includes actual cost to manufacture. It doesn't include overhead costs for the seller (who often doesn't actually manufacture it), the landing costs, etc. True manufacturing costs, including all of that, often are about 3:1 for direct sales and more like 5:1 or more for something sold through a dealer. Some companies also inflate retail in goofy ways. I won't name names, but I had something sent to me from a Chinese company that sells on Amazon. It's retail is it's selling price because it's only available from one place. However, going by the price sheet they sent me and the claimed "retail" price, the cost to a reseller is 1/20th of the retail and 1/10th actual price on Amazon.
I know of two direct sales manufacturers of speakers and subwoofers who use parts that are either off the shelf or marginally modified. The retail price of their goods is less than 10% above the cost for you or I to buy those same parts and build the same product. Most of their margins is simply the discounts they get on the materials. My opinion is that makes them a very good value compared to other products, but it also gives them very little profit.
I've been trying to get a soundproof door manufactured for a few years now. Since I can't manufacture this myself, I need to have it made by a door manufacturer for me and resold through both myself and other dealers. I've met with a number of experts on this and the formula given to me for producing and selling this door was the 5:1 ratio if it is to be marketed by resellers as well (and that is actual direct manufacturing cost, it isn't intended to include all other expenses in operating a business). In my case, I wanted the door to sell for $500, but it is impossible to produce the door for $100. In fact, so far, it is impossible to produce the door for less than $500, and it isn't a good value at $2500 retail.