Well, I have the whole run - AF15 and then ASM1-700, plus everything after 700 up until now, plus I have all the Annuals and most of the (significant) cross-overs with Spidey on the cover. I think the key thing to do is hopefully find a nicely priced run - I was lucky to score a beauty run (many of which where in the 150-400 range) for $600 about 12 years ago on eBay. Of course, not likely in 2018, but still it's the way to go I think, eBay still has some long ASM runs for sale from time-to-time.
I completed it several years ago and still have everything, and I just literally pulled out 150-400 two nights ago, all raw, and "graded" them myself. I figure all 8.0 and higher. But WOW those covers just always blow me away. I would say go for it, it is an awesome run, and I don't see $$ on this run going anywhere but up (so many 9.0 to 9.4 in the 200 to 400 range that are all like $30 here, $50 there when looking them up on GPA - no way I paid that much way back 10 years ago ....)
My suggestion, and what I've been doing, is slabbing all key issues (as someone above suggested) and leaving all others raw (so say anything that is currently valued at north of $200 I'm slabbing).
It is just too cool to be able to open up a book and thumb thru it, and like I said, issues 150-400 have so many awesome covers/stories.
And takes up less room this way - can't imagine how much space 1000 slabbed comics would take up .....