> or a global shipping service, or some SaaS app on the ethereum blockchain, then my customers will have to pay more or less (or my costs will be higher or lower) depending on how active the network is.

Only if you want to have these applications fully running on the base layer, which is frankly nonsense.

To give you one practical example: Storj can provide a object storage service at AWS scale, and its pricing has nothing to do network activity and the price of storage does not change based on the amount of transactions per minute. Unless you want to be paid in real-time and account for every byte that you are storing and transmitting, there is no need to put all of the business logic in the blockchain.