well I am slightly surprised. there is a 'little' difference between prime brokerage relationship and single trading account.
You get quite competitive conditions at DB based on 20 m for all inclusive package.
I do not know a single bank which would refuse something like 500m ........ that includes DB, Barclays, Citi or JPM (I like their execution platforms).
If they do, it is definitely not about the amount.......
The difference between BL, Reuters or all the other multi bank platforms and a single bank platform is just in the quality of relationship. I would value a single bank platform higher.
If the concept is fine and the bank can expect certain growth of AUM , there is always the possibility to negotiate....... This relationship for a single trading account with prime brokerage could start significantely lower than 20m. And single account..... well i guess 1 m would do it as well :-) (negotiation could bring the initial amount even lower) not sure why somebody would do it but........
With 500 AUM you get an interbank spreads, credit line, low prime brokerage fees, Execution desk access , capital introduction, and so on. BTW thats what you get for 20......well cap. intro might start higher....