I just want to note that store bought consumables are not needed to *guarantee* a completion. When very difficult raids for their time came out like Lord of Blades and Master Artificer and Fall of Truth many groups used the *brute force* method by supplying the group with consumables not bout in the DDO store but looted through their time playing and also at vendors such as scrolls and potions.
For may people being the "first" to do something is the most important thing for them as a gamer. The cost of being first is inconsequential.
If people find R10 to be too costly they will adjust. But not all people are diving in head first, some are starting at R1 and learning how the system works and building up to the next. Each will do this at their own pace.