This guide gives no numbers, because a number without a specific object, a specific condition and a specific date is not information.
Condition first
Glass does not improve. Bruises, chips, scratches across the dome and heavy repolishing all reduce what a weight is worth, and repolishing in particular can change the profile enough to alter how the setup reads. Damage that would be trivial on a piece of furniture is not trivial here.
Then attribution
A documented maker is worth more than an inferred one, and the gap is often large. This is precisely why attribution should be recorded as what it is. If a seller tells you a weight is something, ask what that rests on.
Rarity, carefully
Rare is not the same as scarce, and scarce is not the same as sought after. An unusual cane arrangement from a maker nobody collects is unusual and cheap.
Fashion
Taste moves. What was expensive twenty years ago is not reliably expensive now, and nothing about a collecting market guarantees that it will move back. Buy the object.