Curtis Samuel 3 years 30MM is a great signing but Joe Mixon 3 years 27MM, 13 guarantee is horrible?

Am I missing something? Why is paying 10 million a year for a 600 yard reciever who may already be over the hill a great signing for the Bills but an extension for a Mixon with a quick out is horrible? I feel like fans have gotten so accustomed to thinking running backs need to be cheaper than half a sandwich that they are seriously overexaggerating the impact this has on the team even if it doesn't turn out perfect. Even leaving aside my own bias that I still think Mixon can be a game changer and a culture tone setter along with CJ, this contract is really not that big of a deal.

The cap just increased 13% this year alone and this extension doesn't even hit until 2025. This amount is not a big deal for what could be a difference maker.