We study the stellar, brightest cluster galaxy (BCG) and intracluster medium (ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with median redshift z = 0.9 and mass M 500 = 6 × 1014 M⊙. We estimate stellar masses for each cluster and BCG using six photometric bands, the ICM mass using X-ray observations and the virial masses using the SPT Sunyaev–Zel'dovich effect signature. At z = 0.9, the BCG mass $M_{\star }^{\mathrm{BCG}}$ constitutes 0.12 ± 0.01 per cent of the halo mass for a 6 × 1014 M⊙ cluster, and this fraction falls as $M_{500}^{-0.58\pm 0.07}$ . The cluster stellar mass function has a characteristic mass M 0 = 1011.0 ± 0.1 M⊙, and the number of galaxies per unit mass in clusters is larger than in the field by a factor of 1.65 ± 0.20. We combine our SPT sample with previously published samples at low redshift and correct to a common initial mass function and for systematic virial mass differences. We then explore mass and redshift trends in the stellar fraction f ⋆, the ICM fraction f ICM, the collapsed baryon fraction f c and the baryon fraction f b. At a pivot mass of 6 × 1014 M⊙ and redshift z = 0.9, the characteristic values are f ⋆ = 1.1 ± 0.1 per cent, f ICM = 9.6 ± 0.5 per cent, f c = 10.7 ± 1.1 per cent and f b = 10.7 ± 0.6 per cent. These fractions all vary with cluster mass at high significance, with higher mass clusters having lower f ⋆ and f c and higher f ICM and f b. When accounting for a 15 per cent systematic virial mass uncertainty, there is no statistically significant redshift trend at fixed mass. Our results support the scenario where clusters grow through accretion from subclusters (higher f ⋆, lower f ICM) and the field (lower f ⋆, higher f ICM), balancing to keep f ⋆ and f ICM approximately constant since z ∼ 0.9.