There are a lot of variables here to take into consideration, at least for me personally. The intricacy of the bondage and the ropework, the level of nudity and explicitness, what kind of tickling we are discussing (upper body vs pussy, or even what kind of tools). And there's also for me personally a consideration of how long you want the video to be--the longer the duration is, the harder that is on my body, and the more draining it is.
If you want a pussy tickling video with an electric toothbrush for thirty minutes with shibari ropework bondage, first, that is awesome, but second, that is going to cost more because that is more physically, mentally and time demanding.
And keep in mind, tickling videos generally require at least 2 people, so that is going to make these customs more expensive than some others. Then you have editing on the back end. There is a lot of work involved in the whole process, especially to put out a quality product. I think $10 per minute is a totally reasonable place to start discussions for a custom, with prices potentially going up from there.