the difference in 3d printers and servers is rather hard to compare: different servers can compute the same result, faster, slower, but it'll be the same. not exactly true with 3d printers, where a result isn't binary.
Servers aren't actually binary, either. Your cheap server might serve the same result (binary), but performance might degrade under load more rapidly (nonbinary), the failure rate might be be higher (nonbinary), and the support for cheap hardware might be nonexistent (nonbinary). There's also the issue of SKU drift/mix as your cheap hardware fails and gets replaced with a different/newer SKU (adds maintenance cost, is also nonbinary).
At the end of the day, the cost difference plus the ability to mitigate/hide the problems via software makes the commodity hardware the winning option, but it's not just a matter of "same bits come out; good enough".
Commodity hardware is also not really cheap. These are 1U/2U servers that cost thousands of dollars. These are cheap relative to mainframes, but they're not consumer devices.
At the end of the day, the cost difference plus the ability to mitigate/hide the problems via software makes the commodity hardware the winning option, but it's not just a matter of "same bits come out; good enough".
Commodity hardware is also not really cheap. These are 1U/2U servers that cost thousands of dollars. These are cheap relative to mainframes, but they're not consumer devices.