Are Diagrams worth buying at the current price?

I need three Diagrams and a Master Piss to finish off True Draco Metal Kozmo, and currently only have the means to purchase one of those four cards per week. In spite of the OCG list, people haven't been spooked into selling, so the price is still pretty up there. If we do get a banlist in August, I will only have been able to play the deck for a month or so, if I do purchase them. Is it worth it to buy them and possibly take a huge L or should I just convert the deck to Kozmo Metalfoes and just try to play that for Links?

TL;DR: Buy Diagrams and MP once a week for 4 weeks and possibly catch a banlist, or don't buy and scrap True Kozmo Metalfoes