I think that the minimum limits is $500/week, which is represented in the following (paying 50 dollars to 10 Hero/Legendary members), and then appointing a manager will increase the expenses, but it will give better results.
You can run it for one month or two then decide if you want to continues or not (so 2K-4K.)
Generally $80 per member and 20 members i.e. $1600/week will give good results if you hire a smart manager.
Even though you've hired a smart manager, if there's no high quality posters at the moment since they've joined the long term and high payout campaign, the manager only can get the best of low quality posters.
$50/week for Hero/Legendary members are considered a low payout since average of signature campaigns pay around $70 for Hero/Legendary members, moreover the campaign already run at least 30+ weeks.
If the @OP want to get high quality posters, he need to give a guarantee at least 6 months the campaign will run and the payment for Hero/Legendary members is $100+