No, its not a waste of money..

Because barely needs to be better than nothing, and it is actually pretty fair for a significant element of the game.

It is comparatively cheap and highly effective at adding another survivable hit to the majority of unpleasant encounters with AI Scavs. A safety factor of +1 is all you need to seek cover, as soon as you learned to rarely stray far away from suitable cover where one of the simpler-minded inhabitants of Tarkov could be around.

Because what are most of them going to hit you with? Very often, cheap subsonic 9x18mm PM or 20 gauge buckshot. The sort of flying metal not designed to completely overcome the modest protection the PACA vest offers.

Plenty other rounds in the game - but not plentiful in the hands of simple bots. Note that the other kind of flying metal will still be mitigated to a higher degree than simple "removes N bullets from the equation" maths will let one imagine: weak vests can still be useful by chipping off a tiny bit of damage off a single, non lethal torso hit, so another two hits in less dangerous places and their bleed(over) damage become less immediately threatening.

.. but it might still be a waste of time.

If you are not sticking to the play styles where this is common enough to be worth the extra clicks. Almost all players and advanced NPCs will almost always adapt their ammunition and other choices to maximize their effectiveness in surviving PvP encounters by being the first one to inflict lethal damage. Whether that is simply shooting more of that Pst gzh, or using ammunition that negates the effect of simple wearable armor - PACA less reliably helps against players.

Then again, players will also rarely give up 9 spaces in their inventory to take away your armor, so you are buying it for essentially the price of insurance and repairs. The monetary upkeep may be lower than the opportunity cost of the clicks it takes to ask Prapor for the 11th insurance of the day. And you will see that thing a lot in your insurance returns, because you are still best advised to drop it as soon as you see something better.

Mostly Pointless

I did some calculations, comparing thorax hits with no body armor to thorax hits with PACA.

The results are as follows: Out of 137 different types of ammo, the PACA does not add a single more shot to survive for 51 of them. That is 37% of all ammo types in the game. Furthermore, for 29 of the remaining ammo types, the number of average shots survived more than without any armor was one shot or less. That is 21%.

So for 56% of all ammo types, the PACA merely adds one extra body shot. For the price of the armor, that is not good performance. To put this in data: The median increase of survivable shots for the PACA ammo was 1.0.

However, there were some kinds of ammo, where the PACA did offer significant protection: 20x70mm and 9x18mm.

For 20x70mm, the PACA increased the amount of hits taken from 1 to 3 for most types of ammo. Paired with the slow fire rate of the TOZ, this greatly increases survivability.

For 9x18mm, the average hits survived with no armor is 2, regardless of the specific ammo used. The median of survived hits with PACA armor is 7.8 instead of 2.0, with the lowest being 2.1 for PPM ammo, and the highest being 10.0 for SP8 and 9 P ammo respectively.

While this sounds amazing in theory, many 9x18 weapons are also fully automatic with a high firerate, such as the PP-9* variants and the AP* pistols.

Summary

For the majority of cartridges available in the game, PACA offers either no or only extremely limited protection. This is true for many of the commonly used cartridges by entry-level players (available by LL1 traders or commonly found):

• 5.56x45mm M856 (+1 round)
• 5.45x39 BP (+0.1 round)
• 7.62x39 PS (+0 rounds)
• 9x19mm Pst (+1 round)
• 12x70 7mm (+1 round)

The only time the PACA adds a significant factor for survivability is the TOZ-106 shotgun, as well as the Makarov pistol, which are somewhat common on Scavs. For all other guns, the PACA performs very poorly.

So if your explicit goal is to hunt Scavs and you wish to remain lightweight or on a budget, then PACA armor can be useful. In all other situations, it is a waste of money and body weight.

Just for comparison, the 6B13 assault armor, which can be found somewhat regularly in raid or bought from Ragman LL2, has a median increase in survivable shots of 7.5 instead of 1.0.