The Story of Construction Material Balancing
The robbery job outputs materials at the fixed rate of 40% nails, 30% bricks, 20% concrete, and 10% steel. The uses of construction materials, however, have never been proportional to the formula.

For a long time, PEs were the main place where materials went to. But PE's have a different ratio. If one did all of their own robbery to build a PE, they'd end up with around 200-300 extra bricks, concrete and steel by the time they had enough nails. So unsurprisingly, nails were expensive as the bottleneck, steel had very low value, and bricks/concrete were kind of in between.

To balance this, when the smuggling update came out, the steel needed to build and upgrade submarines was massively disproportional to robbery outputs (up to 3x as much), nails were pretty close, and bricks/concrete were under. As a result, steel shot up in value and concrete/bricks became very cheap.

To balance this, when the luxury compound update came out, bricks were a disproportionate cost in building them and building/upgrading the docks parts, leading to them skyrocketing in price. The current situation is of a high brick brice and rough parity between concrete/bricks/nails, although concrete is likely to keep falling because it's overproduced for every current major use.

To balance this...

	Nails	Bricks	Concrete	Steel
Job Output	40%	30%	20%	10%
PE Construction	47%	28%	17%	8%
Sub Upgrade (Tier 1)	41%	16%	16%	27%
Sub Upgrade (Tier 2)	39%	16%	16%	29%
Sub Upgrade (Tier 3)	36%	17%	17%	29%
Compund Construction	31%	52%	13%	5%
Docks (All Upgrades)	30%	49%	15%	6%

construction material ratios vs updates

I think you get the point, it's an endless cycle of updates balancing other updates, all of which ultimately leading to some kind of over/under production and needing to be updated again.

The Game Design Question

All this lead me to the question - what's the point of having four different construction materials - compared to the just having one? It makes building stuff and balancing the economy more complicated, but what does it add in exchange? Does it enchance gameplay in any way?

I generally think that meaningful choices deepen the game. A lot of recent updates have created interesting tradeoffs that allow players to pick between multiple, equally valid paths based on their preferences. You can become an expert reviver (and get the Medallas for it) but you have to sacrifice 20k energy in the gym. You can invest in production prestiges early, but you have to cut down your premium alcohol use for some time. You can get those prestiges unlocked faster by grinding standard jobs for rep, but you lose out on the money you'd make from robberies. You can use Cannabis/Hustle Pills to make more money/progress on jobs faster, but you fall behind on coke energy etc.

The four construction materials offer no such meaningful tradeoffs. You can't pick which ones to focus on making from robberies, and you can't really make meaningful choices on how to spend them. You can't build alternative houses using different material ratios or focus on different upgrades.

There's always been one bottleneck material depending on the latest updates (nails -> steel -> bricks) and you're going to have to buy/farm it eventually, with the only meaningful choice being how long you wait to do so.

Construction Supplies - The Single Item Solution
For these reason, I'm proposing the adding of one single generic material, called Construction Supplies (CS). Construction Robbery will output the same number of items as before, but they will all be Construction Supplies. Properties, submarines, upgrades would still take the same amount of items, but they would all be combined into a single requierement of Construction Supplies.

For example, a Luxury Compound that costs 6k nails + 10k bricks + 2.5k concrete + 0.9k steel currently would simply cost 19.4k Construction Supplies (CS).

This would simplify balancing the economy and gameplay, without removing any meaningful choices.

The Conversion
The conversion from legacy building materials to CS could be done in a number of ways. Job output and building requirements could change immediately but converting existing stock doesn't need to be.

My suggestion here is adding the option to Carlos Construction in Town to convert an unlimited number of legacy materials to CS. While a 1-to-1 option might be the simplest, it would disproportionately favour holders of low value excess materials (like concrete) and punish people who just spent their bricks. Following the job production ratios (1 Steel : 2 Concrete : 3 Bricks : 4 Nails) would also produce results very far off from current market reality.

To keep things simple but fair, my suggestion is to follow the current market ratio of 1 brick being worth about 2 of everything else. This would make the exchange rate be 2 CS for 1 brick and 1 CS for 1 concrete/1 nails/1 steel, which would be a reasonable tradeoff for people who spent a lot money on bricks following the recent update. The Carlos Construction conversion option could stay open for 3-6 months to give everyone the chance to exchange.

As for the legacy items themselves, I would suggest keeping them in the game as a Collectibles rather than fully removing them. Anyone choosing to hold on to some of their old items could show off their Ancient Bricks, Ancient Concrete, Ancient Steel and Ancient Nails years down the line, to prove they are the real OG.

TL;DR
The four construction materials are unnecessarily complex and a balancing nightmare. Merging them into a single item would allow players to build stuff more easily and more quickly, make future economic updates featuring constructions more accessible to all of the playerbase, and reduce the large price fluctuations associated with them.