My take here is very simple. This has all already been discussed at great length. If one wants a way out of his commitment, there is plenty of leeway in Halacha to find (a legitimate) way out. Especially in this scenario where BGs are offering a laughable commission compared to the actual value. With that being said there is an ethical mensch side to all this, plus the concept of honoring your word at all costs. Last year I took a significant hit on a few coins with PFS, on one of the deals. I sent it all to them without hesitation (reluctantly obviously because I wanted the higher price, but confident that I was doing the right thing). The reason is simple it has always been a 2 way street, they have never reneged on anything afaik. This years $3000 coin that no one wanted, they took the five I opted in for and paid commissions. They demonstrated that from their end as well a word is a word. That is the key, if they always honor their word on their end by definition our agreement is a much stronger commitment. This applies to any honest group/dealer not just PFS.
When a BG has already demonstrated that they don’t give a damn about you. They will change the price on you if it drops, force you to return at their own discretion, nickel and dime you for every cent etc..... they have already clearly shown the value of their commitment to you. I believe there is no issue in treating them the same way and relying on the various ways to get out of it. Their agreements have zero value in their own eyes as per their actions. /end rant.