The size of the puncture is one of the most important factors that influence the cost of patching. Obviously, larger punctures require more material and possibly specialized patches to effectively seal the damage. Naturally, the larger and more specialized the patch, the higher the material cost.
But labor costs will also be higher on bigger punctures because the process might involve additional steps that take more time. For instance, the technician might need to reinforce the damaged area using multiple patches, which could double the repair time. And since labor is very expensive nowadays, this could lead to excessive patching costs.
For extremely large punctures, patching might not do the trick. In that case, you will need to replace the tire with a new one, which will cost much more than the patching itself.