I actually got a little curious about this so I generated a 'as_unity_build' module to see how much code there would be without duplicate symbols. Must be a case of a bored late-night Monday I guess. :P
Compiling an "in house" release build on Visual Studio with '/MD' and removing the whole program optimization option ('/GL') results in a final object library size of 1.3 MB. (I should note that for full public release builds you generally want link-time code generation, as this allows the linker to do many extra optimizations at the cost of longer link times.)
If anyone is interested here is the cpp file:
// as_unity_build.cpp
// Builds the entire angelscript library simply by compiling this single file.
// *note* This should be the only .cpp file that is compiled; do not include any others.
#include "as_atomic.cpp"
#include "as_builder.cpp"
#include "as_bytecode.cpp"
#include "as_callfunc.cpp"
#include "as_callfunc_arm.cpp"
#include "as_callfunc_mips.cpp"
#include "as_callfunc_ppc.cpp"
#include "as_callfunc_ppc_64.cpp"
#include "as_callfunc_sh4.cpp"
#include "as_callfunc_x64_gcc.cpp"
#include "as_callfunc_x64_mingw.cpp"
#include "as_callfunc_x64_msvc.cpp"
#include "as_callfunc_x86.cpp"
#include "as_callfunc_xenon.cpp"
#include "as_compiler.cpp"
#include "as_configgroup.cpp"
#include "as_context.cpp"
#include "as_datatype.cpp"
#include "as_gc.cpp"
#include "as_generic.cpp"
#include "as_globalproperty.cpp"
#include "as_memory.cpp"
#include "as_module.cpp"
#include "as_objecttype.cpp"
#include "as_outputbuffer.cpp"
#include "as_parser.cpp"
#include "as_restore.cpp"
#include "as_scriptcode.cpp"
#include "as_scriptengine.cpp"
#include "as_scriptfunction.cpp"
#include "as_scriptnode.cpp"
#include "as_scriptobject.cpp"
#include "as_string.cpp"
#include "as_string_util.cpp"
#include "as_thread.cpp"
#include "as_tokenizer.cpp"
#include "as_typeinfo.cpp"
#include "as_variablescope.cpp"