Cost ranges from about 10 cents for a simple abstract to hundreds of dollars for proprietary financial information. NlightN started 1990. No, but possible for free access also.
Price depends on database used.
Yes 576 different commercial databases from citations to fulltext, from newswires to dictionaries. Varies very much. Lycos database representing Internet is quite old. Updates of commercial databases vary very much. Uses database structures of excixting databases.