Who pays the merchant fee?

I understand that merchant fees are an important aspect of cryptocurrency transactions, but I'm curious about who actually foots the bill. Is it the customer making the purchase, or is it the merchant receiving the funds? Are there any cases where the fee is split between both parties? And if the fee is paid by the merchant, does it impact their pricing decisions or profitability in any way? It would be great to get a clear understanding of this aspect of cryptocurrency transactions.