Harbinger #1 was available and sold rapidly for about $8 in the late 1990s on Ebay. There were about 5 buyers who used $8 as their "floor", and who basically had no limit to the number they would buy, so it was generally $8 or more. Except for sellers who didn't realize they could easily get more than a dollar, it wasn't found very often in the bargain bins. I regularly saw Harbinger #7 and up in the bargain bins... with a few lucky finds of #3, #5, or #6... but rarely.
The coupon in #1 - #6 is often cut out, and the spine is often split (#1 cover paper isn't great).
CGC 8.5 sold for $72 this month, and there aren't many early 1990s regular issue books that can say that.
CGC 9.6 is about $260, and the last CGC 9.8 was $750.
They were also readily available in dust covered back issue long boxes from LCSs and local shows at $1 or less in 1999-2001 on a regular basis (along with all other pre-Unity, late run/last issues, and the Gold/Platinum/VVSS variants).