I've proven to myself that you cannot buy the 10th item..... I stopped at 300 open attempts...
Here are my event 5 results, unaudited.
Vaccines x 9, at attempts; 1, 10, 13, 15, 20, 36, 49, 68, and 153.....
$100K x 23
$500K x 21
Grunts x 25
Supply Frigate x 15
Sea Cannon (Cannon Fodder) x 18
Fortified Sniper x 7
Mech Rover (no bad stats) x 11
300 Valor x 16
Sorry x (Classified)
Total Med Kits acquired 136, via PvP 84