I'm going to give a counter view on this, seeing as it was a forum like this that actually helped me to make a more informed decision for
me.
Prior to my 2006, 330i e90, I had no experience driving or handling run-flat tires, nor did I know that they were more expensive (I gathered they were) and that they cannot be repaired. So, I researched and got information from various forums and websites which encouraged getting the insurance. Initially,
I was against it myself
but after getting 3 tires replaced in
less than three years, I'm so happy I did. No cost, no frustration and totally worth it.
I see you got a 328i Luxury Line, and the lowest price on a run-flat I found was $200 for a Pirelli P7 and that depends on if you got that particular one. If not, it'll be somewhat more expensive. Typically the tires will not be that price, they will be marked up at the dealership, plus you've got to account for labor and the mounting of the wheel. Total will come out to roughly $300.
In any case, this is my opinion and hopefully good advise to you. I'm happy I went with it, essentially it's the "price to play" for getting run-flats. You never know when you might get a flat, and if you happen to be as flat prone as I seem to be over the course of 5 years you'll probably need at least 5 replacements.
P.S. if you really want to make it worth your while, nobody tells you can't put a nail in your own tire for a replacement,
it's not ethical 
but if that's what it takes for you to see a "value" you've got to do, what you need to do.