Balancing powerful items by building cost is borderline unworkable in Minecraft because the amount of resources in any given world is practically infinite - even the non-renewables are so plentiful that no player will ever be able to consume them, even if he plays in one world for his entire natural life. As a result, making powerful items more expensive simply ends up making it aggravating to use, while not actually being any real hindrance to their construction and doing absolutely nothing for balance.
Example: Soul Shards in 1.4.7. Tier 5 shards were extremely broken, balance-wise. Granted, it required a massive investment of playing time (also a resource) to build. But you know what? Everyone and their grandmother had one anyway. Or ten. And every single one was just as broken.
Better balancing methods:
- Limiting power. Resisting the urge to implement gamebreaking features, or making an item with very powerful features have inherent, unmitigatable drawbacks. An example is the Flux effects of Thaumcraft 3 that you get if you screw around with powerful magic too much.
- Infrastructure and upkeep. Fuel needs, energy needs. Railcraft's chunkloaders are an example. You can litter the world with them without breaking the server, because only if you constantly invest effort to keep them supplied with enderpearls will they actually work. And beyond a certain number this becomes too much of a bother for the player to deal with, which limits the number anyone's willing to build. Plus, if the player stops playing, eventually they run out of fuel and stop taking up server resources. And the personal anchor variant even only chunkloads (and only consumes fuel) when the player is actually online. It's a great concept because it allows you to make powerful items publicily available while having them self-regulated by their very design (and also more interesting game mechanics wise than just "build, place, forget").
- Limited use. Making items consumable, non-repairable or accessible only in limited numbers at once. A concept that I've always wanted to see was some kind of "usage license" for certain things. Let's stick with tesseracts as an example: what if a server admin could grant and/or sell "tesseract licenses" to players? Each license would allow for one extra channel/frequency to be used at the same time, with any number of tesseracts connected to it. A player could buy a liquid license to bring in lava from the nether, and later maybe repurpose it to transport biofuel instead - but not both at the same time. He'd need two licenses for that.
That way the server admin could mitigate the "distance doesn't matter anymore" effect that item/power teleportation has on worlds, but still let players access the convenient and powerful tesseracts. A good admin could set his players interesting challenges ("Bring me a boss trophy from Twilight Forest to prove your worth!"), or make prices scale by number of licenses ("The first sample is free... after that, not so much"), or even require taxation ("You can have this energy tesseract license if I can hook into it to power pointless but fancy things at the world spawn hub to impress visitors").
Ideally it would be possible for the admin to control this ingame via commands or a special block. Is that maybe something that the CoFH social features could support, King Lemming?