Bibliofind is very fast and allows to register for a wanted book. You can then calmly decide whether you want to contact the seller for this book for this price. Bibliofind changed hands, and that's probably why it is once again searched by Bibliofind. Nevertheless, using Bibliofind directly is absolutely worthwhile because of its book registration service. Fragmenta Selecta regularly publishes catalogues on Classics and the Middles Ages which are sent as booklet or e-mail and which can be checked at their homepages.
Prices are quite okay.
The most important German bookseller on Classics. Habelt sends catalogues in printed form or as e-mail and has them on his site. Prices are normally quite okay. . Catalogues by e-mail or on their homepage. Paperbacks are often extremly cheap.