Slow code is slow, no matter in what language. Fast code is fast, no matter in what language. The difference between two languages is just a constant factor that becomes neglectable as soon as the application has to scale (e.g. handle millions of items instead of only a handful).
Unfortunately, fast computers nowadays give the illusion of fast although poorly written code, when ignoring scalation. That's why many people can't program well anymore, they just produce unscalable code.
Of course Python has some startup time. But why care as long as the application is responsive? I know enough C code stuff that is worse.