Your implied odds equation does not cover all the factors. The question you asked was about a turn decision. Then, implied odds involves calling a -EV turn bet with a good draw like for a high flush and winning a big pot on the turn 1) if you hit else you fold , 2) bet/raise big 3) villain calls and 4) the hit wins.
Your equation only covers some of these factors and does not relate back to the turn decision.
For a fairly complete implied odds analysis, assuming you have a good draw on the turn, the factors are:
Turn pot before villain bet
Villain bet
Hero call amount
Hero chance for river hit
Hero bet amount if a hit on the river
Villain calls hero’s bet or folds
Hero wins with a villain call (a loss is termed reverse implied odds)
Then, Implied Odds (assuming villain calls river bet)
= Total Win Amount/Turn Investment = (Turn Pot after Villain Bet + River Bet)/Hero Turn Call
Below is an example of such an analysis written in Excel VBA, which determines the future bet you must make to break even.
I did a number of analyses with set, straight and flush draws and found that the conventional statement on needed implied odds of 15 to 1 is not unreasonable for a number of common situations.