The official PAX twitter account notes that PAX East is "down to the last 500" tickets for Sunday, March 24. Three-day passes sold out last year and tickets for Friday and Saturday have been sold out for a while.
Take this as your final warning if you have any intention of attending the Boston event, being held March 22-24. Grab a Sunday ticket here. Tickets aren't likely to last the next 24 hours.
Update: And it's sold out!