You don't need a page number for a citation from a dictionary; just cite the edition and editor of the dictionary, and the name of the article (and the name of the article author, if given).

Is it true that Logos prices are fixed by the publishers who are nervous of losing sales to the electronic versions?

I've heard from a friend in publishing that Logos always argues for the highest discount it can get, but it doesn't always happen. Again, in the Logos product much labor is undertaken to make footnotes and references immediately available electronically with drop down windows, search capacity, etc.