So, quite a large amount of egg on my face as I'm realising now that I didn't explain this properly and actually mixed the two sides up. Ho hum. Shame on me. Anyway, and fortunately for all concerned, Jamie has already been lynched, so I will try to clarify the situation:

The highest anyone was willing to pay for a credit was $400,500.

Person X came along with $63,750,000 and decided to offer $425,000 per credit for 150 credits. 

Person Y sold their 150 credits to Person X at $24,500 per credit above the previous market value. Good for them, no problem there.

However, looking at the other side, the market leading offer is always eventually taken and therefore Person X cost themselves 9 credits in the transaction by not just listing $1 higher than the current market value, which is stupid.

Even more damaging though, and why this angers me so, is that if Person Y hadn't bought those credits, Person Z would have come along and matched Person X's offer or increased upon it, as usually happens. The error of Person X is then compounded and leads to unnecessary inflation in the credit purchasing markets.

Who are these people and why do they do it?