I think Perun would agree that it's better not to be attacked but unfortunately you don't always get a choice. Since you don't get that choice, you have to stockpile interceptors anyway, even though they're not nearly as effective as a good attack.
Part of this is the sheer expense of hardening everything. If you're trying to protect a single airplane, putting it in a hardened hanger is a lot cheaper than trying to get enough interceptors in place that you're going to protect it for sure. However, if you protect that one airplane, they'll just attack the one next to it and they'll get reasonable effects onto that. Or if you protect the whole airport, fine, they will just go attack something else.
The defense equation is not about the cost of the interceptor versus the cost of the missile. The equation is the cost of whatever the missile is going to hit versus the cost of the interceptor. Thus, although interceptors are very expensive, they tend to be cost effective anyway when you consider that they can protect a lot of different unhardened things.
Part of this is the sheer expense of hardening everything. If you're trying to protect a single airplane, putting it in a hardened hanger is a lot cheaper than trying to get enough interceptors in place that you're going to protect it for sure. However, if you protect that one airplane, they'll just attack the one next to it and they'll get reasonable effects onto that. Or if you protect the whole airport, fine, they will just go attack something else.
The defense equation is not about the cost of the interceptor versus the cost of the missile. The equation is the cost of whatever the missile is going to hit versus the cost of the interceptor. Thus, although interceptors are very expensive, they tend to be cost effective anyway when you consider that they can protect a lot of different unhardened things.