It could be emptied out after 400 coins, not 900. If there is already money in there it would take a little more, not much. Unless my math is wrong. https://news.ycombinator.com/item?id=16226641

Reproduced here with more columns, assuming initial price of .02 ETH per coin:

  +----------+----------+-----------+------------+-------------+
  | numCoins | coinCost | coinValue | sell price | Profit/Loss |
  +----------+----------+-----------+------------+-------------+
  |      100 |        2 |      0.01 |          1 |          -1 |
  |      200 |        6 |      0.02 |          4 |          -2 |
  |      300 |       14 |      0.04 |         12 |          -2 |
  |      400 |       30 |      0.08 |         32 |           2 |
  |      500 |       62 |      0.16 |         80 |          18 |
  |      600 |      126 |      0.32 |        192 |          66 |
  |      700 |      254 |      0.64 |        448 |         194 |
  |      800 |      510 |      1.28 |       1024 |         514 |
  |      900 |     1022 |      2.56 |       2304 |        1282 |
  |     1000 |     2046 |      5.12 |       5120 |        3074 |
  +----------+----------+-----------+------------+-------------+

Also the guy said he has 200 coins to use whenever he wants