Nah, they're not linked. That is, if the entire planet had 0 transactions for the next 24 hours, you'd still award bitcoin miners the same block rewards every 10 minutes for the next 24 hours. In other words, block rewards are not a per-transaction cost, they're a systemic cost.
And that cost is dropping. Money supply is just inherent to bitcoin's design to kick it off, but it's dropping to near zero within a few decades, unlike systemic costs of printing fiat which remain endlessly.
The long-term reward are transaction fees, and those are certainly quite cheap. You can move millions of dollars with pennies of fees, or you can make one transaction with thousands of outputs, also for mere pennies. Those fees can stay low as when you get 1.000x more transactions, you can pay for the same security with extremely small fees per transaction. (i.e. securing the system is expensive, again it's a systemic cost, but securing each individual transaction isn't, that's just a cheap process of verifying a signature and storing 1/10th the amount of data of a tweet. So if you get enough transactions going, securing the system can be funded by very many very cheap transaction fees. And if you don't get many transactions going, then bitcoin isn't popular and well used anyway and who cares then if it doesn't work? It's like saying Myspace has technical flaws, nobody cares if it already failed to become popular that it would also have failed for technical reasons.
Bitcoin is imo unlikely to ever let you buy a cup of coffee using a single blockchain transaction (I mean, you can now, I'm talking sustaining this over the long term). Instead, it'll be used as the value network on which financial systems are built that will allow you to do this. Whether that's sidechains or offchains, they'll all use bitcoin's blockchain as a settling mechanism, without forcing low-value transactions on a permanent global ledger.
And that cost is dropping. Money supply is just inherent to bitcoin's design to kick it off, but it's dropping to near zero within a few decades, unlike systemic costs of printing fiat which remain endlessly.
The long-term reward are transaction fees, and those are certainly quite cheap. You can move millions of dollars with pennies of fees, or you can make one transaction with thousands of outputs, also for mere pennies. Those fees can stay low as when you get 1.000x more transactions, you can pay for the same security with extremely small fees per transaction. (i.e. securing the system is expensive, again it's a systemic cost, but securing each individual transaction isn't, that's just a cheap process of verifying a signature and storing 1/10th the amount of data of a tweet. So if you get enough transactions going, securing the system can be funded by very many very cheap transaction fees. And if you don't get many transactions going, then bitcoin isn't popular and well used anyway and who cares then if it doesn't work? It's like saying Myspace has technical flaws, nobody cares if it already failed to become popular that it would also have failed for technical reasons.
Bitcoin is imo unlikely to ever let you buy a cup of coffee using a single blockchain transaction (I mean, you can now, I'm talking sustaining this over the long term). Instead, it'll be used as the value network on which financial systems are built that will allow you to do this. Whether that's sidechains or offchains, they'll all use bitcoin's blockchain as a settling mechanism, without forcing low-value transactions on a permanent global ledger.