If you assume BYU would get 70-80% of what a full member gets they already make effectively the same money already before a negotiation on the new BYU ESPN deal. Remember that the 7M figure is an AVERAGE through 2031 and is backloaded. It’s going to be a few years before they hit that number.
It’s unlikely that BYU is losing tv dollars on staying put.
For a full invite that travel cost would be huge and in the millions.