You're in my head... I had gotten Alien Soldier a few days before your original post, and not long before that I had gotten Contra III.  I had them on my wishlist for a while and finally pulled the trigger.  I got Contra III (didn't include obi) for 8280 so it might not be that much more than you bid.

I didn't know about Alien Soldier until years after I started collecting and I never saw a Contra III on ebay in the far past or recently. I didn't look for Contra III on YJ for a long time because I had a CD-R. It is stubbornly elusive, more so than other Konami albums, but at least it doesn't go into the 20,000 yen territory like so many of its era. I think for every listing of Contra III, there are probably 10-15 listings of each Perfect Selection album. And Axelay (another I want) is listed at least 5 times as much as Contra III, based on my dead reckoning.

I was fortunate to find Alien Soldier listed since I wasn't seeking it out at the time; someone had listed a bunch of Treasure albums and I put my biggest push towards that, though I was really hoping to win Yuke Yuke Trouble Makers as well (outbid while at work).

You will see Axelay more often than Contra III, but it seemed like a lot of times it was simply being relisted since they were starting at over 10k yen.
As far as classic Konami goes there are some albums I would grab if I saw at a good price, but I'm mostly looking for Konami Game Music Collection Vol.5 (which I missed a chance to get a good price and now I'm regretting it) and The Legend of the Mystical Ninja (which I'm not sure I've seen listed under $200). Neither are particularly common to appear either...