They do on the TV (and, I assume, radio) news. But even they sometimes stumble over them, which leads me to further assume that the announcers only speak that way on the air.

Well, not the near-undecipherable real deal[1] Stadin Slangi, but just ordinary contemporary colloquial, I guess.

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[1]: Near-half (old-fashioned) Swedish, near-half (old-fashioned) Russian, a tiny smattering of (old-fashioned) Finnish.

So "seiskafemma" is just the digita concatenated; "seven-five" in stead of "seventy-five". Doesn't feel all that weird to me. For one thing, other languages do that too. And for another, it's all the "-kymmenen" bits that are too long to pronounce, so leaving them out (when that doesn't introduce confusion, of course) seems eminently sensible. Really not weird at all.