How much better is the EOS 3 over the Elan 7?
A few specs from the Canon Camera Museum
EOS 3 - 45pt AF with an f/8 centre, the same as every 1D and 1Ds before the 1DX. (But the EOS3 had eye-control AF, 1-series didn't)
EOS 30 (Elan 7) - 7pt wide-area autofocus, still eye controlled. Apparently faster than the EOS3 eye-control (probably because it had less points to choose from?)
EOS 3 - 4.3fps, 7 with grip
EOS 30 - 4fps, (not grippable?)
EOS 3 - interchangeable focussing screens (I've just put an EC-Civ in mine). 97% coverage, fixed diopter (buy interchangeable eyepieces for different strengths)
EOS 30 - fixed screen. 90%x92% coverage. Changeable strength diopter (like most dslrs).
EOS 3 - 9 exposure bracketing. +/-3 EVcomp. 1/200 X-sync. 18 custom functions. No flash.
EOS 30 - 9 exposure bracketing. +/-2 EVcomp. 1/125 X-sync. 13 custom fucntions. Built in flash.
So at the end, the 3 looks like a decent upgrade from the 30 (elan 7), mostly for the AF, interchangeable screens, and viewfinder coverage. These days the price differential is not much (seeing as a 3 is $150-200 shipped, a 30 can't be much less), i'd still go the 3.