DM's are free to handle in-game item shopping however they want.
Yes.
I think it's going to be hard to escape the idea that this is a fairly high-magic world. Whether we like it or not, we've got +2 weapons popping up already (Alex has one). In a year, it might be +4 weapons. Who makes those?
LEW had as a guideline the idea that there were few to no high level NPCs in the world; that the PCs should be the movers and shakers and big shots. That worked okay, as far as it went, but it had a fairly profound effect on a lot of things, and I think in the end it got pretty uncomfortably stretched and implausible, as PCs got higher in level.
I think it would be better to assume a plethora of NPC classes, and that NPCs can be fairly high level in those classes. I wouldn't bat an eye at the idea of a veteran blacksmith with a reputation for making magic weapons, be considered a 15th level artisan, or whatever. Useless in combat, but he can make swords pretty well.
Personally, I think there's good, established in-character reasons for Daunton being pretty well supplied with heroic tier items, and probably paragon stuff as well, though it may be harder to find. After all, Daunton was the headquarters of
The Five for many years, who we've carefully avoided specifying an exact level for, but were probably at least mid to high paragon. Surely they would have attracted some skilled craftsmen to the area to meet their needs. Since their disappearance, Mayor Brunt has actively encouraged lesser adventurers in the city; surely his encouragement would have extended to purveyors of magic items, as well.