Marbleboy,

It seems you're mixing up a couple of numbers, or maybe I just wasn't clear in how I used them.

In the first example using my method I would come up with the following:
I need to pay $50 and I think my odds of winning are 4.11 to 1 against - I need to win $205.5 for calling to be profitable. $150 is already in the pot to be won, which means I need to win an additional $55.5 on later streets on average for calling to be profitable.

In the second example, using my method and your odds (not the OESD observation as that is 8 outs and your odds seem to indicate a gutshot and 4 outs) I would come up with the following:
I need to pay $80 and I think my odds of winning are 11 to 1 against - I need to win $880 for calling to be profitable. $280 is already in the pot to be won, which means I need to win an additional $600 out of the villain's stack on later streets for calling to be profitable. As an aside the pot after me calling would be $360, which suggests that to win $600 more I would need to win more than one bet.

The method came from me wanting a quick way to assess whether my villain had enough money behind for me to ever be able to have implied odds to call. If you take the amount you need to call and multiply it by the odds against you winning and the amount you would need to win is bigger than the pot and the villain stack combined - it's pretty much never a good idea to call. Everything else sort of followed from that basic observation.