Thanks!

Do you have a proposal for how to display the new calculation of cost to the player?

Perhaps in the industry fund menu?

Using your example, the fund menu should show 'Forest: cost £150,000,270'?

What exactly should be shown in the menu? The price for tile clearing will differ depending from the chosen place to place (pun intended). The clearing costs for a 12-tile industry planned to be built on only grass tiles will be different from the clearing costs when 5 of the tiles are populated with one tree each or from the costs when two if the tiles are populated with three trees each and one with four trees.

The overall cost is unknown until the moment one have chosen the area to place an industry. That said it would make IMHO more sense to create a popup dialogue that asks "Want you really build [industry] for [overall cost]?" or to calculate the price with the highest possible clearing cost per tile in mind (building cost (max) = industry_cost + clearing_cost).

I do think that for some players it is vitally important to solve the display issue.

When funding an industry, an industry that's worth a spend of £150,000,000 might not be worth a spend of £150,000,270. Or it might be worth a spend of £150,000,270, but not £150,000,540.

The cost shown really must match the cost incurred. It's an effective principle in UI design (WYSIWYG).

Therefore to satisfy the accurate cost goal, we really must have a way of calculating the actual tile cost in the industry fund menu.

One option would be to limit industries to only build on certain terrain types. This can already be done in the newgrf spec, and we could patch the default industries to do it?

Another option would be to normalise all terrain clearing costs. So that clearing costs the same for all land types.

Another option would be to remove the cost of clearing land.

Another option would be to remove the ability to fund industries.

Removing the cost of clearing and terraforming land for industry construction could be a good enough solution. The remaining cost of already so large you can easily imagine it just contains the cost of land preparation. Additionally, some industries represent open-pit mines, and having land clearing cost included separate for those is frankly pointless, the industry is already digging a huge hole in the ground.

Perhaps something like this?

When you build an industry, the cost to clear the land is still included in the total industry build price, which remains the same as previous. But, the cost to clear the land is filed separately, in "Construction" instead of in "Other" (which is where the actual industry building cost is filed in).

1. Use the BaseCosts newGRF to set "build raw industry" to x32.
2. Set the game setting for the build raw industry mode to "As other industries".
3. Start a new game.
4. Cheat in exactly £150,000,000 and repay your loan.
5. Do not do any other actions that affect your money.
6. Open the fund new industry menu and select the "Forest" industry.
7. Attempt to build the industry.
8. Building the industry succeeds and sets your bank balance to 0.
9. Look at the financial details window.
10. You should see a cost of £270 under "Construction" and a net income of £270 under "Other". (The net income of £270 is made up of the £150,000,000 obtained using cheats and the cost of £149,999,730 for building the industry).

Removing the cost of clearing and terraforming land for industry construction could be a good enough solution. The remaining cost of already so large you can easily imagine it just contains the cost of land preparation.

And nobody is going to fund an industry, then magic-bulldoze it to "cheat" and terraform without paying.

Maybe there is some real gameplay value to 'clearing' having a cost, and that cost varying (rough grass and stone are obstacles that you may want to avoid), but I agree that if the menu says it costs 150M, it should cost 150M. However I probably would never notice the discrepancy. Early in the game, the cost difference between building rail on grass vs. stone vs. foundations can be devastating. However, the game never warns you of this, nor even lists a price for a piece of rail. Most construction actions seem to silently add the land clearing cost, whereas funding an industry works more like buying a train with a listed price.

As the player doesn't 'own' the industry, I generally thought of the funding as an inducement to an industrialist to build it themselves. They are actually taking on the cost of the buildings and land, just as if you were to prospect.

Some bad ideas:
Leave it as is. getting free bulldozing with your 9 figure purchase is negligible.
Silently add the land clearing cost, but change the price description to "150M plus addl. land costs".
Hide industry costs. Player can use shift click for cost estimate.
Only allow industry building on player owned land (would have to allow selecting layout)

It would be much simpler to just remove industry funding.

It would absolutely achieve the goal of accurate costs in the most reliable way.

We could also then clean up elements of industry NewGRF spec and GS API. Deleting code almost always will have the extra benefit of reducing the defect count.

Closing as it would be not intuitive/user-friendly otherwise.