But, it's save you more.......
If the section you are playing are on the cold section. Let's say more than 500 spin without bonus, and you spend 0.2$/spin we can guess around 20-30% your money back from the normal spin hits. Meaning you spend 70-80$ for the normal spin without any bonus at all, by bonus section you save your self with the bonus 2-3x times buys.
It's not about the profitable return, but saving cost spending for the spin.
Yes, that's a good example, but another thing I want to say, I choose a spin at number 70 and I will stop it at number 50, aka in round 70 I only play 20 spins and I will repeat it up to 3 times like that. That's the pattern I play, often I get 50x from Olympus and also several times the 500x multiplier drops suddenly and also often get fs in manual spins in those 20 spins.
In other words, your calculations are correct but for me running 500 spins normally is not a tactic to find victory. Well, back to round 70 to 50, aka I play 20 spins that I repeat 3 times, if that doesn't get any results I will switch to another slot game.
It is true, save in expenses would be more appropriate if made a FS purchase than a 500x spin, but I was never interested in buying fs.