1969 lawrence g. roberts wrote a forecast about the costs of hardware and software replacement and how to calculate them. two years before he has written the first design paper on arpanet

Software Costs All of the conversion programming must be completed during the overlap period since it is usually unacceptable to suspend any portion of the work for more than a few weeks. In order for this to be true, the level of programming support during this time must cost at least A/m dollars per year. If m is less than n, this level of support would normally be retained until the next procurement cycle working on the new work. Some of the new work can be done during the overlap period, thereby eliminating some of the pure conversion workload. However, since rethinking the program takes longer than just recording it, the total overlap period workload would be increased, not decreased.(Data Processing Technology Forecast, April 23, 1969

another paper also including the costs, this time of delivering data

Cost per megabit for Various Communication Media 1400 Mile Distance", 1971 Telegram: $3300.00; For 100 words at 30 bits/wd,daytime Letter: $3.30; Airmail, 4 pages, 250 wds/pg, 30 bits/wd Mail DEC Tape: $.20; 2.5 megabit tape, airmail Mail IBM Tape $ .034; 100 megabit tape, airmail (The Arpanet, 1971