If you accept the premise from the post that minimizing support costs acts as an incentive to enhance usability, then i think there's an important factor you're

If you accept the premise from the post that minimizing support costs acts as an incentive to enhance usability, then i think there's an important factor you're touching on here. Since many open source organizations provide FOSS software and charge for support, they've got less of an incentive to provide easy to use software. Rather, their model is tuned to providing easy to support software.