It is my view that, given the massive increase in demand for sought-after bottles in recent years, purchases of such limited parcels should be limited to one (or a maximum of three, depending on supply) bottle. I am sure that we can all name recent cases where a wine has disappeared practically as soon as it has gone on sale. I have found this frustrating on many occasions.
Limiting purchases to one bottle per member seems to me to be really the only way that members can have a better chance of being able to try these wines, especially those who do not regularly buy very expensive wines from the Society,
Allowing richer members to buy larger quantities (some of which will inevitably be sold on, often at a tidy profit) seems to me to be fundamentally against the ethos of the Society.