Exchanges treat data as a product with tightly defined usage categories. Showing a quote on a screen to one human is one licence; feeding the same quote into an automated system is a separate and much more expensive non-display licence; redistributing it to clients is another again.
Traders meet this as a stack of small monthly line items on a brokerage statement, and firms meet it as audits and back-billing when usage is misclassified.
Example: a retail trader pays roughly $2 to $15 a month per venue as a non-professional-status subscriber. The same feeds classified as professional non-display for an automated strategy can run into thousands per venue per month — a cost that alone rules out some strategies at small scale.
Related: non-professional-status, direct-feed, securities-information-processor, exchange-fee