I think it is more relative. If a dog sled costs 6 Gp, which is not having any seats, and has just 2 runner, a small platform and a hand rail, I'm going to compare with an arresleigh that is more substantial, having sides, seats and a teamster seat. The comparison would be that I think the sleigh might be more expensive because of production time, materials and extra embellishments.
Also I think you might be wrong when you say that the tables also factor in the historical periods and the availability of materials. Of course buying a dog sled in the Sahara is not going to be at the regular price, but a sleigh will be made near a region of permanent cold and would be in scale to a similar, but smaller item, available in that same region.
But I am extremely biased on the subject as I am making a complete system of goods and goods production. I am hoping to correct the ridiculous prices appearing on the ICE tables, in fact, every equipment list in the entire history of RPG, except a few notable exceptions such as Harn master.
Speaking of the harn master tables:
Sled, cargo 80d (pennies)
Dog, sled (the animal) 50d
Wagon: 200d
People can consider these prices as researched by others and can draw their own conclusions.
Game on