Here are my two cents, both as a fashion lover and a journalist.
Even for being a reporter at a major metropolitan newspaper, Lois dressed a lot nicer than many of her real-life counterparts. I worked at a paper that would compete with The Daily Planet in terms of circulation, and most of the reporters wore slacks and nice tops, or even jeans and sweaters. Only the upper management wore suits and the like on most days. And don't even get me started on copy editors such as myself ... Most of them (not including myself) figure that they aren't going to be seen outside the newsroom so they wear whatever the heck they want, including sweatpants. No joke.
I can see Lois wearing some nicer heels that she got from Nordstrom or Macy's, but nothing more expensive than that, since she does a lot of running around and going undercover. I figured the shoes she ruined in "Ultrawoman" were a nice leather pair, but nothing designer. While Teri Hatcher is definitely a Manolo Blahnik kind of girl, Lois is more likely to wear heels that she can chase bad guys in. I actually have a black strappy pair of heels VERY similar to the ones she wore in the opening scene of "Lucky Leon," and they were about $80 at Nordstrom. Most of the truly designer shoes -- Blahniks, Stuart Weitzman, etc., have VERY high heels.
As for the clothes, I can also see Lois buying a few nice suits a couple times a year at the aforementioned department stores starting from the time she got hired in her early 20s because she wanted to make a good impression and be taken seriously. I actually have a book about TV fashion and L&C had a section and Judith Brewer Curtis, the show's costumer, said that she dressed Teri in a lot of Calvin Klein (including most of her coats) and pieces from Barneys New York's signature collection. But here's the catch -- I don't think the viewers were supposed to THINK Lois was wearing designer clothes. They just happen to look and fit well. Kind of like how the most basic T-shirts that the guys on "Friends" wore could have been $250 a pop. The designer and price was for the actor, not the character. And Lois wouldn't likely be able to afford Prada or Chanel -- we're talking about purses that are, on average, $3,000. I could, however, see Ellen having something by one of those designers -- and Lois having contempt for what she would likely see as a shallow display of materialism. I mean, seriously, the woman doesn't even carry a purse half the time, just a briefcase.
Oh, and this is a side comment, the average salary for a reporter in New York that Shane posted factors in that some of the biggest newspapers in the country -- Newsday and the New York Times and Post -- are there, and that doesn't say whether those are reporters working for papers IN New York, as opposed to just living there, i.e. reporters who work for the Wall Street Journal in New Jersey. That is going to significantly up the median salary, as opposed to other states.
