Your question needs more clarification; development of what, and maintenance of what:
std::cout << "Hello, world!";
That code cost more (time) to develop than it will to maintain, and some 'real-life' trivial/one-function applications are the same. Others are not; things like web browsers/APIs/etc need to follow changing standards, but that should be seen less as maintenance than it is further development.
In an ideal world one released version of an application shouldn't need extensive maintenance - if maintenance means patching, covering holes, or fixing bugs; because good development should include a period of very, very detailed testing; and it should be based on well-considered plans.
The real world isn't an ideal world by any means; but program code is a complete infallible unit; it shouldn't break down like a lawnmower; because it isn't subject to mechanical stresses.
That is, perhaps an opinionated view; but it's the best reply I can give for such a general statement..
thanks alot mattEvans..
but iam doing a project for this statement, ur right that it might be general but i will explain it,,
the s/w developers responsibility doesn't end when a peace of s/w is implemented, delivered, and installed ,, while in use errors are discovered and changes are needed so u need to add new functions..
so this is exactly what i mean by maintenance my question is why it costs more than development??
i know that it makes sense but i need a professional explanation based on software engineering .. wish that u get my point
During initial development you don't have to provide releases, or patches, or documentation, or support to anybody outside of the development process. You can correct bugs and add features quickly and easily en mass. After the product has been released, you don't have these luxuries, and they all have a significant cost.