You can lose more than 75%. If there's no ETH in the wallet they can't pay you back out.

I made a spreadsheet to figure this out and the reason I dont mention that risk more is that is only at risk of happening after around 900 tokens are sold - until then the contract will always enough ETH. If 900 tokens are sold, the contract will have over $100k worth of ETH which I really hope never happens.

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

Yeah about that... you're about 17 tokens away there.

Well that escalated quickly

Hey, you can only lose up to 100%, right? As long as this thing shoots up at least 101% you're guaranteed profits!

You can lose 100%, but hey, you can gain 100 000%