The basic costs of a bonding system are in the voltage supply and vacuum
chamber + pumps. If you don't need vacuum, then you only need the power
supply and a hot plate. A supply capable of 1000V will work, but you may
want to get one that can do 1500 or 2000. The hot plate should go to 500 C
but you can get away with around 350 with some materials.

bonding technique for mems device in high vacuum

Look for papers on "Room-temperature bonding" for descriptions of bonding
in high vacuum. Usually in an epitaxial or STM vacuum system with an ion
beam to "clean" the surfaces by removing the top layers of material. You
should make sure that your materials don't out-gas significantly at 10^-9
either or your devices won't sustain that vacuum. Most systems that will
pull 10^-9 are baked out for a couple of days anyway so the requirement of
200 C for 2 days shouldn't be a problem.

Mike