Go-go high-flyers like Motorola Inc have to keep exceeding expectations or their shares go for a Burton, and profits up 30% on sales up 21% just aren’t good enough, so the shares were off $4.50 at $64 by the opening yesterday. The main cause for concern was that Motorola said growth of the cellular telephone subscriber base is moderating somewhat in the US and Europe, although it is expanding in other regions. Growth in wireless communications, semiconductors and advanced electronic products was highest in international markets, it said, adding that average US cellular phone selling prices fell faster than in the past last quarter.