dosage of high 20% protodiocin tribulus per day?

i posted about tribulus and got advice of using 4-5 grams per day.
my query is i was of the opinion that you needed a tribulus product with not only a high steroidal saponin% but more importantly a high protodiocin content.

i purchased TRIBESTAN and also thermolife's TRIBOSTEN both these products are concentrated to give 20% protodioscin content they come in 250mg caps and recommended dose is 1-2 caps 3 times per day(750-1500mg/day).
at 4 grams that is 16 caps per day.a box of 60 costs $25.this would only last 4 days making it very expensive.
surely when people state 4-5 grams/day this is for the herb tribulus and not a concentrated extract.i have seen bulk suppliers selling 100grams of tribulus for $8 ,i would assume it is this type of tribulus that needs to be taken at 4-5grams/day as it would have a low protodiocin %.

any help would be greatly appreciated.

anyone??