Imho, what the O/P describes is something like how car dealers are usually more expensive for an auto part rather than internet sellers or the local Autozone/O'Reillys/Advance etc. Car dealers have overhead in running parts departments as they are expected to hold quite a bit of inventory of parts to service cars of that brand--holding inventory has costs as does paying the guy at the counter to answer the phone, order parts not in stock, their knowledge, and get the parts from the back. Spoilage can also be an issue as some plastics and rubbers deteriorate over time. The cost of maintaining the square footage of the dealer's parts warehouse also comes into play.
An ebay seller may be operating out of a house, selling parts from an auction, etc., and the parts may not be returnable if misordered by the buyer. A seller may also simply be clearing out junk that he would receive nothing for if he did not sell it online. To him/her,any revenue at all is good because the other option is throwing it out for zero money.
Ebay does impose a certain fee on transactions and maybe shipping costs and now is subject to state sales taxes as per the recent Supreme Court decision. Smaller sellers for now are escaping this, but state and local governments have an insatiable appetite for tax dollars which probably will cause the large online exchanges to force sellers to collect the taxes for the smaller sellers. Expect to pay taxes on most if not all online purchases in the future.
Internet wholesalers can address parts, labor, and inventory costs by locating in cheaper parts of the country and have a whole country to sell their wares to which lessens dead or slow moving inventory holding costs--this is why some mega car dealers now have substantial online parts sales. You will be paying sales tax on these purchases now as well. Commercial entities are not going to take the risk of tax liens from distant jurisdictions to save their customers a few bucks in taxes.
Shipping costs are separate from this as they are from third parties but no company is going to eat these costs in the long run and if they offer "free shipping" then you are paying for it in the total price paid. Right now the USPS is relied upon for a lot of this cheap delivery with express companies handing it off to them for the actual delivery to the customer. The USPS is also broke and getting broker--expect shipping costs to continue to rise as a fair portion of it is labor and fuel is an unknown variable cost. The cheap shipping from China is also coming to an end as the Trump admin forced the International Postal Union to no longer consider China as developing and thus people buying parts via Amazon or Ebay directly from China will have to pay more as the U.S. Postal Service will be allowed to charge market rates for these shipments (which should ease their deficit a bit). Don't expect it to be cheaper on shipping from China than from other states as was the case.
To sum up. As the manufacturer, Remington has to keep a large number of parts for their firearms in stock, have knowledgeable parts people, pay for the warehouse and shipping costs. Some of that parts inventory is necessary to provide warranty work on firearms and the other is because people expect that they will be able to get parts from the manufacturer for their purchases. Would you buy a firearm at full price knowing that you could not get parts for it in the future if any break?
A warehouse requires rent, light, maybe heating/cooling, and general maintenance. There are holding costs on inventory (local property taxes apply to inventory btw) and using your money to stock inventory means that you cannot use it elsewhere, spoilage, and obsolescence. There is a reason that Smith and Wesson or Colt no longer work on certain firearms or sell parts for them as they sold their parts inventories of old models to places like Numrich. The holding costs for these parts exceeded the revenue expected from them for the manufacturers plus the prices were constrained below a profit making margin because of disassembled parts from old guns floating around. The rise of Ebay means that you are also now competing on price with individuals who have cheaper costs in selling and consequently price their goods lower (the smarter business like ones base their prices just below the mfg. so that you pay nearly the same amount).
