Actually, due to the memory management strategies that the Java language (or any other managed language) makes possible, object creation is little more than incrementing a pointer in a block of memory called the young generation. It's much faster than C, where a search for free memory has to be done.
The other part of the cost is object destruction, but it's hard to compare to C. The cost of a collection is based on the amount of objects saved long-term but the frequency of collections is based on amount of objects created... in the end, it's still much faster than C-style memory management.
