Basic (stupid) question about pot odds

[Shandrax]

Let's say I do sports betting and it takes me 10$ to bet for a possible return of 40$. I get 40$ for 10$ = 4:1 pot odds.

Now in poker what I don't understand is this:
Assume there were 30$ in the pot and one guy bets 10$ to offer me a 40$ pot that takes me 10$ to play for. That usually goes as 4:1 pot odds in the literature, BUT when I call the bet I have to put my own 10$ in the pot also! In contrast to other forms of betting, my own money raises the overall pot that we are playing for. If I win, I get 50$ and since that bet costs me 10$, aren't my pot odds 5:1 instead of 4:1 then?

Stuff like that keeps nagging on me, so I have ask it here and I am willing to take the risk that people think I am an idiot [img]/images/graemlins/smile.gif[/img]