To be honest I think you got your data wrong. And I do not know why you have it wrong, my best guess is you are sending from exchanges instead of doing a real bitcoin transaction. Exchanges bulk their orders together to get better pricing. Sometimes, you can get a 15 minute bitcoin transaction, it happens. Other times I have waited 30 minutes.

Here is the site showing the empirical data on a bitcoin transaction:

https://bitcoinfees.21.co/

"For the median transaction size of 226 bytes, this results in a fee of 58,760 satoshis." 58,760 satoshis for the median transaction size is a cost of $1.46.

At a $1.46, most addresses are unspendable, making bitcoin useless for micro-transactions. Here is a news article about the high fees and unspendable addresses: https://news.bitcoin.com/tension-rises-around-bitcoins-fees-unspendable-addresses-and-spam/

I have used bitcoin myself. If we load up the Exodus wallet, they detail the fees for us that I will pay just to make sure my transaction arrives in a reasonable time frame:

For a $15 USD transaction, I will be charged a mining fee of $3.58 USD.

This is a 23% fee on a $15 USD transaction. So your numbers are wrong no matter how we slice and dice it. If I had the better case transactions priced down at $1 USD, I would be paying 6% of the transaction.

You must be doing batch transactions with a 3rd party exchange, the point of bitcoin is to run your own wallet and hold the funds yourself for security. By doing 3rd party exchanges, the funds can be stolen and they are not fully secure.

Here is the data on the average confirmation time in minutes:

https://blockchain.info/charts/avg-confirmation-time

Right now, average confirmation time is 65 minutes. There have been spikes, though and we can just imagine the spikes were resolved by orphaning transactions and jacking fees.