[Bester]

you need to make cmdtext or
dcmd_vbuy whichever you used in your script i will go witg dcmd

and then put the same shop code as Fantje put above
this will make you a command /vbuy which players can use to buy vehicles you added for buying
i give demo below

Код:

new vehicleshopDialog;
dcmd_vbuy(playerid, params[])
{
#pragma unused playerid,params
ShowPlayerDialog(playerid,vehicleshopDialog,DIALOG_STYLE_LIST, "Vehicle Shop", "Stretch\nInfernus\nBullet\nSuper GT\nHotring Racer\nElegy\nSultan\nBF Injection\nJester\nCheetah", "Select", "Cancel");
    return 1;
}

and then put the "public OnDialogResponse" code as above Fantje given