i can give you some premade zombie_costs that i've added myself.
First go into _zombiemode.gsc
go to line 414
If you don't find it search this  // Debris

Now copy what i sent

add_zombie_hint( "default_buy_debris_3000", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_3000" );

you can add as many as you want of these but remember this one is a buy debris section the other one right under has to be

add_zombie_hint( "default_buy_door_3000", &"ZOMBIE_BUTTON_BUY_OPEN_DOOR_3000" );

Add zombie_cost                      It should not say unknown now because you've added more to the script.
      3000
     
Hope this did exact what you wanted

BTW this is the standards

   add_zombie_hint( "default_buy_debris_100", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_100" );
   add_zombie_hint( "default_buy_debris_200", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_200" );
   add_zombie_hint( "default_buy_debris_250", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_250" );
   add_zombie_hint( "default_buy_debris_500", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_500" );
   add_zombie_hint( "default_buy_debris_750", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_750" );
   add_zombie_hint( "default_buy_debris_1000", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_1000" );
   add_zombie_hint( "default_buy_debris_1250", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_1250" );
   add_zombie_hint( "default_buy_debris_1500", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_1500" );
   add_zombie_hint( "default_buy_debris_1750", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_1750" );
   add_zombie_hint( "default_buy_debris_2000", &"ZOMBIE_BUTTON_BUY_CLEAR_DEBRIS_2000" );

Wouldn't that work since a localized string doesn't exist so it would probably show nothing, so you'd need to remove the & and actually enter the string or enter it into the .str file?

Also I don't think he's talking about doors since he said "things".

Then he needs to make his own thingys
Custom strings,
like // Pickup or whaterver else its scripted

trigger = getEnt( "triggername", "targetname" );
trigger thread trigger_function();

trigger_function()
{
    cost = 1000; // Amount
    self setHintstring( "Press and hold &&1 to buy trigger [Cost:" + cost + "]" ); // Setting your hintstring
    while( 1 )
    {
        self waittill( "trigger", player ); // Wait till the trigger is used and get who uses it
        if ( player.score < cost ) // Check if they have enough points
        {
             wait .1;
             continue; // Stops here if they dont have enough
        }
        // continues here if they do
        player maps\_zombiemode_score::minus_to_player_score( cost ); // take the points
    }
}

this looks really useful if i knew what to do with it lol thank you though

Wouldn't that work since a localized string doesn't exist so it would probably show nothing, so you'd need to remove the & and actually enter the string or enter it into the .str file?

Also I don't think he's talking about doors since he said "things".

ZOMBIE_BUTTON_BUY_OPEN_DOOR_3000

Can you be more precise on what you want to do?
is it like you want pickable items to cost or just any trigger of your choice ?