I was looking over some of the values (and I suppose in this day and age they mean less than ever), and mused a bit about the Vicky silver - can you imagine?
One big example in the halfcrowns was the value compare between the 1839 currency and the 1862 and 1864 proof coins; the latter were valued at 1/4 higher whereas IMHO, the exact opposite at higher preservations should be true & that a truly uncirculated specimen of the former might rightfully be valued at double
Another was in the sixpence series where in Unc., 1848/7 AND 1848/6 were valued the same as the 1854! Absolutely again IMHO not so. The former is much scarcer in Unc. than the 1848/6, and both likely pale compared to the 1854.
Another weakness that likely can not be tackled would be a coin such as the 1882 shilling in a slabbed "66" which along with the 1889 SH in like grade would probably have to be unpriced.
In any case, values are relative and in any give sale or auction coins obviously may go higher and lower as we all know. Pegging values is nearly impossible but possibly comparing rarity to some degree might be moreso...