How Much Rust is Too Much?

[JGray]

I have a 71 K5 CST Blazer with similar rust to this one and have been asking myself the same question as to how much rust is too much. I've been trying to get to a decision to restore it, sell it or part it out. I've been told by an individual locally that I feel is pretty knowledgeable that mine is a $2000-2500 truck here in Montana (he was interested in it until he saw it...).

Personally, I wouldn't buy one needing this much work. My problem is I do have some sentimental attachment to it - it was immaculate when I bought it in 1992 and I've lived in three different States with it since then. It looks worse than what you can see in this pic, and I know will get worse if I dive in...