The notion that the JVM is not heavy because it needs less than a GB of disk space seems crazy to me. I consider OpenSSL to be wildly bloated because it is over 1 MB.
The actual HotSpot JVM itself is about 10mb, but that includes 4 GCs and 2 JIT compilers.
The Avian JVM can statically link an entire program and widget toolkit with itself and produce a 1mb binary.
It's not that big a deal. The space gets taken up by all the libraries. But then you'd want to compare a JVM against e.g. /usr/lib on a fresh Linux install ...