It is interesting that CC kept the receipt for as long as he did. I also think it's one of those "things" that only CC knows the reason why and it may never make any sense to us. No matter the argument his lawyers will ~try~ to present. It will be weak at best, imho.
As far as all the other financial stuff goes, I believe that LE/MCS had already done much of that homework before CC was arrested for triple murder. It helped aid/build part of their case. IMHO, CC had only tunnel vision and that was one for only himself. To be that absorbed regarding his wants, needs, "loss", and justification for all *he chose* to do is a person who does not function on a healthy human level. CC is not, in any way, mentally ill. He is walking s.o.b. who has only cared for himself. Sadly, many walk among us. How scary is that???
Thinking about the evidence items found in the house, I believe CC left them there to be found, so that in the event LE ever looked at him for the crime, he could claim he was being framed. He just didn't count on them finding the evidence he tried to dispose of that would really tie him to the crime. JMO