any reason that bronze challenges give 50 points while silver gives 40? silver is harder right?

Sorry, I completely overlooked this thread.

It's this way:
Bronze: 50 Fame Points
Silver: 90 Fame Points

When you already have completed the Bronze level then you get the additional 40 for completing silver so that you have 90 Fame Points in total.
If you don't have completed Bronze, you get the whole 90 for completing Silver (and the Bronze medal too).

You are right, Silver is harder than Bronze and in total you get more points for Silver.