I have no issues with what anyone, manufacturers, distributors, or a 3rd party reseller wants to sell their pin for. It's human nature though throughout any product purchase across all categories. People get angered by high prices, but love to see a great deal that benefits the buyer or them in particular. I may not agree with the price, but it doesn't mean I feel it's unethical. It just means that amount of money would not leave my pocket in order to acquire that particular product. Either someone will find utility at that price or they won't.

It won't. This is a common misconception. Economically it doesn't pan out like this on products across many categories. The shoe industry, which is a billion-dollar industry, is a prime example of this. A manufacturer with their MSRP and amount of stock has to find the correct balance between just having enough product scarcity to drive demand for their brand and price it perfectly to where the end user can still receive a considerable percentage of the product on day 1.

Prices won't rise because a small percentage of buyers are reselling something. Prices can possibly rise because 100% of a product line sold out on day 1.

It seems a lot of people are basing their opinions off mostly Maiden LE since that's the flavor of the month and their concerns for the quick flip practice, but realistically addressing the OP's question, anyone that feels selling for a profit is unethical (I consider this at any point in the lifetime of the pin), are you applying this across the board to used games that are currently selling for well above the original MSRP? Because if so, the majority of anything on the marketplace will fall into this category.

Just looking through the first 2 pages on the marketplace from current distributors and 3rd party sellers, the following rough percentage price increases/decreases are as follows.

600%
85%
183%
-12%
-18%
53%
196%
150%
200%
75%
198%
120%

Iron Maiden LE is 53% basing it off the highest pin for sale which is $13,500. The one in which everyone is blowing up the thread is at 34%.

Economically, resellers do not affect a brand's pricing in this manner.

That's exactly why it doesn't work in this manner. Resellers can't guarantee a product will sell out completely, they're a side effect of high demand and limited supply. If they could create fake demand, every LE and CE would be selling out within 24-48 hours on every pin, but that doesn't happen. That's up to end-user consumers to complete that circle and up to the manufacturer to produce X amount of product at the correct price that is slightly below what demand will actually be for the product. Basically, any business economics class that does a case study on this would come to this conclusion for well-known brands, without resellers a brand would keep supply less than demand.