It is an honorable sacrifice to support the work of those who create good change.
If paying for to participate would be difficult, but not detrimental, it qualifies as a sacrifice. You may have to cut back on other spending (going out to dinner, buying coffee, or a new outfit), but this will not have a long term harmful impact on your life.
If paying to participate would lead to long-term harm - such as not being able to feed your kids, pay rent, or pay for your transportation to get to work, then you are dealing with hardship.