Almost every resort charges you for bringing in your own photographer, DJ, decorator, mehndi artist or caterer. The fee structures differ, the amounts differ, and almost none of it is published. For an Indian wedding, where importing vendors is normal rather than exceptional, this can be several thousand dollars you did not budget for.
The most common. A set amount per outside supplier, sometimes per day rather than per wedding. A photographer, a videographer, a DJ and a decorator is four fees, not one.
Charged per member of the vendor's team. A photography team of three costs three times what you assumed, and second shooters and assistants count.
Less common but very expensive when it applies, particularly to catering.
Most often on catering, for food-safety and liability reasons. Some properties will not permit outside food under any circumstances, at any price.
We could put numbers here that look authoritative, but outside vendor fees are negotiated per contract, vary between properties inside the same brand, and change without notice. Any table we published would be wrong for somebody within a month. What we do instead is get the current schedule in writing for your specific property and date before you sign, and factor it into the comparison between resorts.