I trained for more than a decade at a school before I attended a seminar outside my lineage. Going to extra-lineage seminars was neither promoted or discouraged at our school.
I do think students should be fully immersed in their school's curriculum before wandering too far afield. Of course, it is often difficult to tell how close a particular lineage is to another.
The seminars from which I have taken information and incorporated it in my training are few and between. Kicks are not my strong suit, or even my cheap suit, but working kicks across the floor in your seminar in NY is one that was a take away. Another example is a slight change in a move of a technique from the method which I originally learned increases the effectiveness of the technique. Always, that is what I am seeking: how to make this execution more effective.
I believe the market will bear a $50.00 to 60.00 cost for a two to four hour seminar. One instructor I know breaks the day into three seminars. I think it is $50.00 per class. In that instance ... I think it is too much to pay for the Kenpo. I have paid it for the community; to meet the other practitioners and to support the instructor.
This summer, it appears several seniors are advocating "camps"; two to two and a half day, destination events. Financially, these make no sense for the kenpo. My trip to to the Las Vegas Camp will end up costing me $1200.00 to $1500.00 (camp, hotel, flight, food). Some will pay more, some will pay less. But, this type of coin is not about the Kenpo, but the community. To meet, work and play with Johansson, Bychkov, Halsey, Zaninovich, Epperson, and others, is the justification for travel.
Mr. Sepulveda's camp in New York is a reasonable investment when considering travel from New Hampshire. Five or Six instructors for $500.00 to $600.00 for the weekend, every other (or every third) year isn't bad. This past year, I had a bad experience, and decided to leave that camp early. Had I ponied up any more cash than that ... it could have created a significant resentment. And that wouldn't be good for me, or of the instructors.
Shorter answer to your inquiry, Mr. White ; Be sure the day is filled with effective kenpo, and effective instructors. Total costs of a couple of hundred dollars in direct and indirect spending isn't unreasonable. At least to me.