Differents values at this payment?

[loews]

Hey guys, i'm trying to understand something that just happened. I tried buy a thing from one guy that use "mycellium" as auto-processor of payments.
Its okay i'm buying from him since years, but today something happened.
I have sent $56 worth of coins using 60k fees, mycellium refused to auto confirm my payment because i have send a few cents more than the expected. I have contacted my seller and he said that he just got $50 at his wallet, but i have sent $56 and even with fees this goes to $54, not $50. wtf?
Or i'm getting crazy? Check this https://blockchain.info/tx/b54f0fda26148aaa8968d026768768c7e0ac24a35a5e700fde8be0e1df1b559d

[BitcoinHodler]

you are not using USD to STOP quoting things in USD terms!
and merchants that are accepting bitcoin should give you a bitcoin amount to pay not a USD value.

and every merchant that i have seen so far is asking for bitcoin and wallets also take bitcoin as their primary input (change it if your wallet does otherwise)
and when you are presented with a BTC amount to pay, it no longer matters how price fluctuates. it is like a contract that merchants and customers both agree to within the time frame you are support to make the payment.

[loews]

you are not using USD to STOP quoting things in USD terms!
and merchants that are accepting bitcoin should give you a bitcoin amount to pay not a USD value.

and every merchant that i have seen so far is asking for bitcoin and wallets also take bitcoin as their primary input (change it if your wallet does otherwise)
and when you are presented with a BTC amount to pay, it no longer matters how price fluctuates. it is like a contract that merchants and customers both agree to within the time frame you are support to make the payment.

Guess you are right..