I don't know the price, BUT I know that while it has gotten better, shippernet is still not 100% reliable. Weather can affect it - the EBPC cruise was without shippernet (or at least it was VERY sketchy) because of the hurricanes they had to sail around knocking things out of whack.
So even if it's affordable for the family member, if 100% always being able to connect is a necessity, that cannot be guaranteed.