For my application, I don't need that much pressure on mold. Youre talking for injection molding but I'm in injection-blow molding, my mold is keep hot so the melt didn't get cold so it's require less melt pressure to fill all cavities.
By now, if I'm correct with my mathematic, I need 1.68 tons by square inch MAX, I keep a 20% of safety factor. We rarely goes over 5000 psi on the melt pressure as I caluculate with some real data.
DAMN I love my job when I have challenge like that!!!