I know this wont make much difference, but numbering parallels is very, very expensive to do.
The issue is that there isn't a lot of people who can do this sort of stuff. If you look at Panini, they have invested in the infrastructure to have a couple of machines that solely do serial numbering (they have the work to keep it fully utilised). In Australia, there isn't a huge need and you would struggle to find someone who could do this for you at a reasonable cost.
It's a bit like collating and packaging cards.....only 1 maybe 2 people who can do it locally here in Australia. There just isn't the scale of work to have people specialising in this type of work.
If you do it, it has to be in big enough quantity to bring down the cost, but for a handful of cards, way too expensive.