Yes, some 3D printing technologies take the density of your model into account in their pricing as indicated in this article about how prices are calculated. 

Solid or un-hollowed parts will require more resources (material, energy etc.) and building time, making them more expensive. Additionally, for Powder Based Processes (like Laser Sintering, Multi Jet Fusion, and Metal 3D Printing) there is a limit on the density of the whole building volume which secures the quality of the printing process. This density limit restricts the sintered volume of parts in the printer and thus results in an elevated price for dense parts.

Therefore uploading a hollowed model can lead to a cheaper price. 

What is the effect of the check box “do not hollow”? 

If the “do not hollow” box is checked, the part will be printed as requested and we will not perform a hollowing procedure prior to printing. Please note that printing full or un-hollowed parts can increase the risk of deformation as well as the price of the part.

What happens if I order without checking the box “do not hollow”? 

If the box is unchecked, then our production planning team can decide to hollow out models with higher wall thicknesses to prevent deformation and discoloration issues. Above a certain wall thickness value, models are even hollowed by default, see below.

Default hollowing of parts which are not ordered with "do not hollow"

Please note that above certain wall thickness values, the data preparation specialists in our production will hollow models which are not ordered as "do not hollow" by default before printing. However, once ordered the price will not be adapted anymore even if you do receive a hollowed model. 

This specific wall thickness value for default hollowing is different per material: