If you only buy the spetch, then yes they are expensive. However, the cost of leather has been going down, and if you buy a leather and make the spetch off of it, suddenly cost goes waaaay down in comparison. If everyone is selling spetch (or spetch cost x 5 for leather) for more than what the Leatherworker guild sells them for, then just buy from the leatherworker guild. No one seems to remember that the guilds are selling most of the repair mats too.
It's the more exotic repair materials like the glues that are more problematic.
True, and while I don't buy them, the trip to Gridania to see the one NPC who does sell them often isn't worth it.
I still see plenty of people trying to get an item repaired with horn glue for 1k or so, even though the cheapest I can find it on my server right now is 10k (http://ffxiv.yg.com/item/horn-glue?id=10009315#s).
Yeah, people need to have a better grasp of what the repair items cost before listing it. I'd actually prefer that they list the repair item as a reward. That way, I'm guaranteed to get the item back (so long as I don't botch the repair, but that's always a risk anyway).