In my opinion Code Name Guns prices increased around 22%-44% over the last 2 years. It's ridiculously high for what you get. Yet they are not rare they are not hard to get and they certainly don't guarantee victory.
The only perk to them is that they are open use. That's it.
So making guard systems impossible to move through by unwanted guests would skyrocket the prices, which are already inflated, that doesn't reflect the increase in value.