SMR's non-linear relationship to reality

[nat]

There's often talk around here about how SMR prices are absurdly low, usually in connection with high-end cards. Now, I'm not into high-end cards (because I would like to stay married), so I'm curious about how it does with lower-tier cards. For instance, I recently bought a lot of three low-grade 1933 Goudeys: Lazzeri, Frisch, and Combs. The Combs is definitely poor, which SMR values at $28. Frisch has one big crease, but otherwise only ordinary wear. Let's call it poor as well. $45, per SMR. Lazzeri looks nice but has a big mark. To be as generous to SMR as possible, let's call it poor. Also $45. All raw.

Now it's true that not all poor condition cards are the same, but none of these cards are missing chunks, they don't have any paper loss. Frisch and Combs have been banged about, Lazzeri just has a mark (albeit a large and conspicuous one) and would be VG-ish otherwise. The point: although damaged these cards are not destroyed.

So by SMR this lot should be valued at $118. I won it for $36. And I don't think that I got a deal on it. There were ten others who put in bids. It's just that low-grade cards aren't worth very much. Now I know that SMR is only supposed to be used for PSA graded cards, but it's not like these cards need PSA's blessing to verify their condition: I'm assuming that they're all in as low of a grade as possible. There's also value added by authenticating cards, but the risk here is tiny. Having these cards graded wouldn't do anything for their value.

So here's the non-linear bit. Does SMR over-value low-end cards, and under-value high end cards? And, if so, why the difference?