The OP is absolutely correct: AKIRA is skyrocketing.
Not necessarily just the EPIC version. Anything AKIRA is on fire and will only continue to do so.
I started collecting the EPIC books when I was in middle school, right after I saw the anime at my local arthouse theater. This was in early 1990. I managed to grab up all the back issues at local comic conventions, and continued buying the book monthly. Then things got very sporadic. There were droughts of months between books, and then for no reason, it just stopped altogether. It didn't resume publication until 1995, my senior year of high school! That's a hell of a long wait to complete a 38 issue story. But yes, those last 5 issues after the long hiatus are definitely the hardest to find. 37 and 38 include "tribute" pieces by international comics writer and artists, and those pieces have never been reprinted, not even in the Japanese reprint of the EPIC books.
For a long time, it seemed like Japan enjoyed the exclusivity of the early material. The original YOUNG magazines where AKIRA was published in serial form are insanely rare. First of all, only the savviest of nerds would even think of stockpiling the thick 400 page weekly books, especially when any storage space is a premium in tiny Japanese apartments. Second, the book are printed on the cheapest of cheap newsprint, and they'd need to be very carefully taken care of to survive Japan's humidity. On the rare occasions you'd see the first AKIRA in YOUNG issue for sale, it's always in terrible condition and pages frayed and yellowing. It's a miracle any survived at all after 40 years!
I spent most of my time in Japan grabbing up anything by Otomo that I could afford. At first that meant going to the big manga stores in Tokyo, but eventually people started selling more and more stuff on yahoo japan auctions, and mercari. That's what opened the floodgates.
A few years ago, I'd see the first AKIRA going for $2-300. These days it's been pushed up to $2-3000. International fans are rabid for AKIRA, especially in France and America. These collectors have now turned their sites on owning the original magazines, and there simply aren't enough to go around. Japanese collectors are upset that they're getting outbid left and right by foreign buyers that have inflated the price to ridiculous highs.
I was very lucky. I snagged two of the most desirable YOUNG magazines before the foreign boom came in. I think I only paid about $50 for each. But that was a wonderful investment. I never want to sell these, but if I had to, I'm sure these are gonna be worth a fortune someday. In the entire original run of AKIRA, it was only featured on the cover FOUR times. I own two of those issues.
So I believe those original YOUNG issues are a great investment...IF you can find them.
As for the original Japanese printing of the 6 volumes (tankoban) that collect the whole series? I don't think the prices will ever get crazy on those. Those exist in the millions upon millions. The first volume has over 100 printings. I'm not aware of any American comic book that has 100 prints. Imagine trying to collect all them, having to check the indicia hoping for that 57th printing your missing. I think that first printings of these may eventually become sought after, but just owning them at all is no big deal cause there's sooo many circulating out there.
So the TL;DR to my rambling post is this: AKIRA is hot and it's only gonna get hotter. That includes the EPIC books of course, but more so the insanely scarce original YOUNG magazine run.