They're each right, or probably more accurately, not wrong.
Most industries have a "customary" discount structure. It appears what you're attempting to do is back into a pricing structure, not having established one at the beginning.

Most retailers keystone (double cost) to arrive at their selling price.

The whole pricing structure has become so convoluted the last 20yrs that there is no single answer anymore. The channel of distribution used to be Mfgr, Distr, Retailer. During each past economic downturn as people scrambled for sales anyway they could get them, the lines became very blurred, then toss in the internet and you have even more chaos.

In my company (we manufacture) about 75% of our sales come from either distributors or retailers. A smaller % comes from the website...we use it primarily for a specialized product that our distr, and retailers don't usually handle. That way we're not competing with them. We first establish our cost. We keep a cost sheet for each product we manufacture...roughly 150. It covers virtually everything that goes into that product, raw materials, components, labor, packaging. We then take that total and keystone it to establish our wholesale price for distributors, that price is then keystoned again to establish the "Suggested List Price" (Retail)
For the Retailers we sell to we discount that Suggested List Price by 40%. We do this because if we come into conflict with one of our distributors we always back away and this allows them to sell them and still make a little money. Given they don't have the cost of pioneering that customer and it just becomes a case of clipping coupons for them they can take a smaller cut. It's not a perfect system but it's worked for us for 20 yrs now. In our case, we have a modest R&D budget that is priced into each products cost...probably not more than a penny or two per item.

The advantage of the cost sheet is that it's updated twice a year, usually May and November. We issue our new prices effective July 1st, and Jan 1st. Before we kept cost sheets we lost alot to price creep. You're costs go up a little on each item, and without even knowing it you're losing profit. When you've got 15 or 20 different cost components in a product, it doesn't take many going up to knock out a fair amount of profit.

This may not be the best way, but it's one way, and it's worked well for us for 20yrs.
Good luck
Denny