is this a bug or something?

yes, this site is broken ever since they introduced the bundle >$25 max 20% limitation bug.

Bundle games, do a search on them.

Do you gift games only for farming the contributor-value?

sigh games that were in some popular indie bundles or some free giveaways are considered "bundled", marked with asterisk * in the dropdown, and count only up to 20% of your non-bundled value. Except first $25 which count as "normal". Hence if you only give those bundled games, you can get max $30 contributor: $25 that count as "normal" and 20% of that which is $5. Total $30.

this is being asked plenty of times and I suspect you can find this info everywhere around

I don't even...

People that create these threads should be suspended.

Yep.

the search function is well hidden and you'll never find it... ha-haha-ha!