The Grinder requires not-trivial amounts of power, and with a trivially-designed system will almost always cost more (gold, redstone, and iron, in the default recipe) in addition to infrastructure requirements. On versions without tool durability, a Melee Turtle can swing away until the server closes.Or you could just use MFR. Which is what everyone does on all the RR testing servers. Cheaper, more reliable, easier, more options. It is not that big a deal. There is ONE outstanding issue with Dartcraft, but BlueDart is gonna clear that up and PowerCrystals is routing around it anyways.
((And MFR's got a number of good points, but machine cost balance really isn't the mod's focus. It's there so you don't have to think about any of the mechanics it interacts with. Most of the balancing concepts, as far as I can tell, emphasize having to deal with all the piping, energy concerns, and logistical matters.))
If you want it to do /well/, and do it yourself, yes. The systems complexity actually outstrips the code complexity for a good miner, defined by a miner that can self-feed, automatically return to base/a charging station, and carefully keeps itself to a square boundary or focus on specific layers, and handles server restarts, and so on. That is a fun challenge, and honestly the reward is a little underwhelming for what you put into it compared to a Quarry.Except to write the code, make sure its fed, etc.
A bad miner doesn't need to do that. Stripping a small area to bedrock and climbing back up is trivial from a coding perspective, after which you can manually trade items and feed the turtle easily. Putting a bunch of turtles side-by-side, telling them to mine in one direction, and then coming back later, is a very, very simple thing, but simultaneously opens a lot of gameplay space that are pretty questionable.
((And tend to be server unfriendly when it goes wrong, between the fountains of loose items and the potentially wasted material, but that's a concern in most automated mines.))
No, it's not the sort of broken that can cause the game to collapse into infinite diamonds, or anything like that. And there's a lot of really good things that Computers can do, and probably /shouldn't/ be attempted using vanilla. It's more the question of uncomfortable design space, which can negate a number of things in other mods.