Market Board RMT Sellers

[Jojoya]

Not saying that this isn't RMT for sure, however......
Timeworn Map parties, FC's, and LS' are a thing, even an individual can be a map-hound.
While one can only obtain on their own via DoL jobs at a rate of one map a day, one can also obtain as many maps as they can get from trading them from other players or buying them cheaply on market boards.
It seems all the items you listed have some material that is ultimately obtained from a Timeworn Map chest, in various levels of rarity.
It would not be very hard to obtain a bulk of materials from farming Timeworn Maps, producing the glamor items from the materials, then use the proceeds to fund map harvesting, while still turning a profit.
Managed correctly, one could self-sustain a map-hound hobby this way and have a net gain in Gil.

If the player is doing their own map farming, then certainly it's profitable at any price.

The OP claims that the seller is buying the materials off the MB then selling at a loss.

Even if the seller is doing both, I don't see it coming out with a net gain unless the seller is also botting the maps (always a possibility). While the map bots were very obvious in Shadowbringers, I haven't seen any sign of them since start of Endwalker. Common belief seems to be they've moved from map and Eureka bunny farming to general FATE farming to buy gemstone vouchers to sell.

If there is RMT involved with the seller the OP is talking about, we're missing part of the picture.

You want to tell us that a Player who made a lot Gil in the past, never invested in his Char / Jobs / FC and has now a pure Heart of Gold? Since years this Player is selling 700 and more Items on a Server he/she is not even Playing on. Just to give to the poor and make them happy?

We don't know what other characters the seller has. A lot of players set up dummy alts just to avoid potential harassment.

I can't say RMT isn't involved but I also can't say that it is involved with the information the OP provided. As I said above, there's information we're missing here.