Actual streets? (I wouldn't recommend buying them from a dude off the street lol)
Or streets as in black market (aka online)?
If the latter, I'm assuming you're talking about a standard 250mg/ml 10ml vial. 500mg/week is just a standard dosing for test. One vial would be enough for 5 weeks at 500mg/week.
Run you about $40-60/vial from a reputable source for test from a well-reviewed lab.