You're right, In such allocation bounty hunters can get handsome amount of rewards undoubtedly, If Team and Bounty Manager planning to pick the real hunters in their promotion. But i see few BM didn’t made the rules that's why most of the time hunters got payment and end of the day transaction fee is more than Bounty payment.
Now every bounty hunter can directly make calculations in general or roughly on each bounty Allocation that has been listed on the bounty page with a predetermined time duration, so that if it is considered to be very suitable with the payment that will be received when the bounty ends, there will be many hunters entered the bounty.
There are several bounties that rewarded with tokens that already in the exchange, so the bounty hunter could calculate how much they work will be paid but also it's not the exact amount because the price of the token could be up and down. I think if bounty hunters joining a new project bounties they must have analyze the project itself before joining because there are many projects ended scam or the reward are not entering exchange after the presale.