Technically the 58 is a ‘5.8cm’. The ‘cm’ is a give-away that it is an older lens, from about 1960-61. As you would expect of a fast optic from that era, it is soft relative to even the less-modern 50/1.4’s from the 70’s. For those that live and die by sharpness, this is not your lens. It has its own character, though, one that I quite like esp with B/W. I rarely us it at 1.4 yet the large aperture makes for better viewing in low-light. The longer fl (16%) makes for less dof at comparable apertures than that of a 50mm, a quality I often use to great advantage. Contrast is less than its modern brethren but that, too, is part of the novelty in a world where 50/1.4’s and their look are a dime a dozen. I have several lenses in the 50-60 range but have a warm spot for the 5.8cm f1.4, not due to its ‘rarity’ (I use the word loosely) but for its more classical rendition.
Is it worth the cost? Hmm...cost, value...cost, value, one of the eternal questions. You may find the 5.8cm to be an acquired taste, or maybe not. I took an immediate liking to it. I don't know the cost current cost but I can tell you all about the value!