or did he say it?

     The 'beautiful is difficult' -  Plato said that did he?
     That occurs at 435c in The Republic, part way through Book 4 in English translations. It is tossed off in passing by Glaucon during an exchange with Socrates. Here you go, starting with the ugly little guy himself:

     But again, a city seemed just when three kinds of nature were present in it, and each did what is its own. And again, it seemed temperate and courageous and wise through certain other affections and dispositions of these same kinds.
     True, he said.
     And so, my friend, we will thus also expect the individual to have these same forms in his own soul, and rightly expect the same names for them as those for the city, because of the same affections.
     Quite necessarily, he said.
     Here again, we have fallen into a trifling inquiry about soul, my friend, I replied: whether it has in itself these three forms or not.
     It hardly seems trifling to me, he said. For perhaps the saying that noble things are difficult [χαλεπά τα καλά] is true, Socrates.
     Apparently, I replied... [translated by R. E. Allen, p. 132].

     Consider, Glaucon, Socrates, and the rest of their party, are engaged in a long and arduous inquiry into the nature of the soul and its formation, or deformation. The City conjured in the long and arduous inquiry, dear reader, is itself a simulacrum for that formed or deformed soul. To thus inquire about the nature of the soul is noble, and beautiful [καλά], implies Glaucon as he offers this gnomon, and, again, noble and beautiful things are difficult [χαλεπά]. Socrates approves.
     Or does he? Plato is the master ironist in his portrayal of the ironist Socrates. I hear a certain tone in Socrates's reply, a combination of astonishment and resignation. One can see him looking down a bit, and almost muttering Apparently. This inquiry will be even more difficult than any of them first thought. So far so good, but can we say unequivocally that Plato says categorically that noble and beautiful things are difficult? I think we can infer that he would echo his master's Apparently, and the whole of his works attest to a love of and a desire for the Good, however understood, and a conviction that the attainment of the Good is arduous and therefore quite rare.
     To reach that conclusion, however, requires that we hear a gnomic saying, woven into a brief exchange designed to shift the dramatic flow of the dialogue at a particular point in the inquiry, in the context of Plato's work as a whole, and The Republic in particular. We must grasp at least somewhat the many modulations of the word καλά. [noble, beautiful, good, and so forth - Philokalia, etc.]. We must, finally, understand that the true danger and difficulty of this dialogue is that it just might lead to greater perplexity about the nature of the soul. If we find ourselves ever more perplexed as to that nature, we will thus be ever more perplexed as to how that soul can be rightly formed so as to tend to the Good.
     We might, in short, end up in a Dark Wood of Error. It is no accident, dear reader, that Plato can seem quite the absurdist, especially in the early and middle dialogues.