One approach to showing value is as follows:

1.) Create a spreadsheet with all of the features of your group's/company's products(s) listed in rows.

2.) Create a column for every team member in the group and highlight the lead developers for each feature.

3.) Then ask each team member to add a checkmark in their column for every feature for which they would be willing to be on hook for 24x7 triage pager duty.

Over the long term - the most valuable contributor(s) on the team will be the one(s) with the most checkmarks next to the features they led development on (i.e. they write understandable code and document well) combined with the most checkmarked rows in their column (i.e. they proactively seek to understand other peoples codebases).