With modern optimizing compilers, it's highly unlikely that a pure C program is going to be all that much faster than compiled .net code, if at all. With the productivity enhancement that frameworks like .net provide the developer, you can do things in a day that used to take weeks or months in regular C. Coupled with the cheap cost of hardware compared to a developer's salary, it's just WAY cheaper to write the stuff in a high-level language and throw hardware at any slowness.
The reason Jeff and Joel talk about C being the "real programmer" language is because there is no hand-holding in C. You must allocate your own memory, deallocate that memory, do your own bounds-checking, etc. There's no such thing as new object(); There's no garbage collection, classes, OOP, entity frameworks, LINQ, properties, attributes, fields, or anything like that. You have to know things like pointer arithmetic and how to dereference a pointer. And, for that matter, know and understand what a pointer is. You have to know what a stack frame is and what the instruction pointer is. You have to know the memory model of the CPU architecture you're working on. There is a lot of implicit understanding of the architecture of a microcomputer (usually the microcomputer you're working on) when programming in C that simply is not present nor necessary when programming in something like C# or Java. All of that information has been off-loaded to the compiler (or VM) programmer.
