We have a winner! Harley has found the truth. I have recollections while working at BVM that the bolt was not and standard bolt, and was custom made to design. The hardening properties are very tight and specific to give the proper non-brittle bolt strength so it won't break, and the proper hardness in the hex so it won't strip. No one wants to have strip or break a bolt when they fire up for a round at Top Gun or the Scale Masters... and a broken bolt could release the fan and result in the loss of and aircraft.
So enjoy your 19 cent bolts, but don't propose they are the same as the BVM ones.
Design a custom bolt with special hardening, and order a few hundred at a time from a quality maker, and see what you investment is!

Dave
(I already regret participating in this circus)