τὰ δὲ περὶ τούτων ἀναλογίσματα πρός τε οὐσίαν καὶ ὠφέλειαν μόγις καὶ ἐν χρόνῳ διὰ πολλῶν πραγμάτων καὶ παιδείας παραγίγνεται οἷς ἂν καὶ παραγίγνηται;
i do not understand the last part: οἷς ἂν καὶ παραγίγνηται;
but the reflections about these concerning [their] being and utility, accrue to those to whom they accrue.