As the MagSafe case is sandwiched in the middle when charging, it is more likely to get hot. So a more resistant to high temperature 150 degrees Celsius SH magnets is better. If you want to know more about grade specification, please visit neodymium magnet grade table.
Usually, consumer goods use more affordable N series neodymium magnets, such as N35, N42, N45, N52 and etc. And neo magnets N45SH and N48H, especially the former, are industrial magnets commonly used in various motors and generators.
High temperature grade magnets are also more expensive due to the use of more heavy rare earths. This may be one of the reasons why Magsafe is expensive. In order to reduce costs, many third-party manufacturers are turning to the strongest room temperature resistant magnet N52.