What makes you think that the merchant covers the transaction cost. The cost of inefficient fiat system is already included in all the goods and services we consume.
Bitcoin fixes this by being transparent and open, while second layer solutions, particularly Lightning Network take care of scalability.
I don't understand what you're trying to say. Most merchants with the exception of maybe gas stations don't offer a discount for cash purchases. Therefore if something is priced at $10 - I only pay $10 whether I use cash or credit. If I use a credit card, the merchant covers the fee. It definitely is not cheaper if I use any crypto currency or network. At least not yet.
No free lunch.
