This is something I've battled with myself.
I'll admit, I was late to the party. I started reading the comic around issue #68-70 (about a year before the TV series) and back then, I saw TWD #1 at comic shows for $350-500. I wish I had jumped at it then.
I have a hard time bringing myself to spend $800+ on a modern book that I feel, at some point, will inevitably slow down... I look at Spawn (not the best comparable obviously as there was over a million printed of number one) but the characters popularity now compared to what it was 10 years ago isn't even in the same ballpark.
I've noticed the comic is starting to wane a little bit. It's still good, and I love the series, but I don't have the same "oh my god, I can not wait until the next issue" that I had before.
As many have pointed out, I don't think this bubble will ever "burst." I'm just not sure it is a $1K book either.