[mayk]

where to put
new SELLCAR1[] = { 600, 671, 689, 571, 861, 751, 1267, 678, 874, 698, 1000 };
a example cmd with this "/sellcar
new rand = random(sizeof(SELLCAR1));
format(string, sizeof(string), "Your %d$, cash.", SELLCAR1[rand]);
SendClientMessage(playerid, COLOR_LIGHTBLUE, string);
GivePlayerCash(playerid, SELLCAR1[rand]);