JImG59 is correct.
The Church funds the use of the Botafumeiro on the days listed - ONLY.
At all other times, and at all other, lesser, religious commemorations and Masses, the Botafumeiro is used IF someone contacts the pilgrim office at:
www.botafumeiro@catedraldesantiago.es (in Spanish)
... and offers to pay for the Botafumeiro to be used at a specific Mass or occasion.
With this subscription, comes preferred seating so you and / or your group can be up front to see it all, without obstruction. That is why most of the paid use of the botafumeiro is by groups.
Those who are making pilgrimage, or who are visiting the cathedral otherwise - even cruise ship passengers bussed up from the port at Vigo for day trips - get front row seating if their host paid for the use of the botafumeiro. But, usually, it is a civic group, church group, boy scouts, girl scouts, a corporate group, the military, etc. who have walked into Santiago de Compostela, and want to be certain that they see the Botafumeiro while they are there.
Don't quote me, but as of last summer, when I worked as a volunteer, I recall the per use price was something like €450. I could be incorrect. Consider that there is an expense to maintaining the Botafumeiro. It is fundamentally a really heavy and precious (solid silver) kettle barbeque on a chain. It needs to be serviced and cleaned between uses.
Also, the men who pull the ropes - Tiraboleiros - are compensated for their partication in this honored activity. Long gone are the days when seminarians or legions of religious men could be pressed into service.
There are perhaps 15-18 of these fellows available when needed. So this select cadre of local men are called on to do the honors.
I consider this all to be rather practical and reasonable.
Hope this helps.
Tom