Like it says above, domains were free until mid 90's. then $100 for the first 2 years and $50/year after that that included the $15/year Internet infratructure fee that was later determined to be an illegal tax. You had to send in an e-mail template (
http://www.tamaramichel.com/etgs/templates/domain-template.txt) but people sent in many thousand of templates a day so it slowed the system down. The delay sometimes hours or even days delay so if you detected a domain dropped there was probably already a template in the system ahead of you. In 1997 NSI issued their monthly reports to the National Science Foundation that said at any given time 50-100K templates were queued up to be processed.
Network Solutions used to invoice the domains but you could use it for a couple months until they took it back. The domains used to drop when they were removed from the billing system effectively giving a real-time drop detection (the whois was a day delay so most people were confused). They used to have 2 drop periods per week I think.
NSI would not change the system because they convinced the NSF that they needed to charge $35 for something that cost them less than $1 to deter hoarding. NSI founders made many millions on this scheme.
Bulk register was the first to open up the competive market at $10/year in 1999. The drop time was changed to 6AM and you had real-time registration instead of the template system. I remeber setting my alarm every day and I also remember picking up 4LLL.com in about 5 minutes that had dropped for total cost of $40.