High-sec only has the basic ores in the asteroid belts (veldspar, scordite, pyroxeres, plagioclase). Due to the prices of minerals, typically veldspar is 70% profit, and scordite, pyroxeres, plagioclase are 95 - 105% (i.e. about the same, depending on daily market fluctuations).
However, it’s possible to get “lowsec” asteroids in high-sec., if you use probes to find ore anomalies, or combat anomalies or sites that have NPC pirates to fight, but also asteroids all over the site. Or, certain agent missions might also have higher-quality asteroid scenery in addition to the pirates you’re supposed to kill. In fact, a couple of the career agent missions are like that, with several million ISK of kernite and/or scordite available. These sites are rare, and because they’re in high-sec, it’s likely someone else has taken the site already, but they provide some breaks in the monotony.