What aside from computers had this much of a price/performance improvement in 30 years?
I think “international phone calls”, “cost of document transfer (contingent on it not needing to be paper)”, “brokerage commissions”, hmm...
(“Brokerage commissions?” Yep; it once routinely cost $100 to $400 to purchase stock on the public markets, because you needed a licensed professional to do it for you. These days discount brokerages are trying to decide whether the single-digit dollars they charge even matter.)
Fun fact: if you haven’t thought of this question before, “What percentage of revenue is the commissions?” is a question you can get out of annual reports for any brokerage, and you are probably overestimating it markedly.