You get the FS100 from the process of enchanting boss gear. I personally got a FS90 from enchanting a couple of TETs. The costs for this FS is included in the repair costs. Of course, you first need to get to this point. For the stacks from 0 to 30 you probably not always use boss gear, that is, the repair costs are likely less. So, for example if your plan is to achieve full TET, you start with a set of stacks appropriately for a TET. You probably build the lower stacks (< 30) as you need it, though. After achieving this TET and also after re-building all the boss items you abused for this TET, you inevitably get new FSs, probably another TET FS which you save for later use. Ideally you end up with roughly the same set of stacks, so that you can start another TET attempt. The costs for all this, are basically the repair costs for all the boss items you used for enchanting plus concentrated stones and the costs for building the lower stacks, where you probably used other items, say green gear, black stones, etc. This calculation is just a rough estimation. What's pretty obvious is, that getting a PEN is quite expensive, where getting full TET is pretty much doable. Whether getting a PEN is doable or not is also a matter of luck. If I can afford three PEN attempts, I may be lucky. If I can afford 25 attempts, I may still be unlucky.