I'm defining extreme pressures as about 2500psi and up
I researched and found that many high pressure hydraulic stuff mention used centrifugal pumps that cant be adapted for air because of their chemical properties so help me brainstorm and evaluate ideas that can be reapplied to create extreme presures
some things I thought of are:
home made air booster, sadly the higher pressure cylinder must be homemade while the lower pressure one is bought

another variation could be a high pressure hydrolic source (possibly used pressure washer to be cheap) converted into air pressure
theres also the idea JSR suggested in mechanizing an existing pump like a http://www.pyramydair.com/cgi-bin/accessory.pl?accessory_id=81 [/url]
but I wonder if this idea or any others may require special cooling like the pumps I have seen