Improved Building Costs Patch
Here is small patch which allow you to change cost of few things in game. For now you can multiply price of tunnels, bridges, terraforming (without building on slopes), signals and airports. You can change multiplier for each in: advanced settings -> Construction -> Improved Building Costs. Its simple but can make game a bit more challenging. I know there are similar grfs but they change price of building on slopes.
Base on Terraform cost multiplier patch made by dptr1988
Second smaller patch is
Additional Tax Patch v0.2(Bigos tax - unofficial name

I made it because I notice that after few years of playing cash flow so quick that you don't know what to do with it and it newer stop to flow. Patch adds tax base on company value.
-> at start ~2 year free from tax
-> ~10% of company value per year after your company reach 250 000 pounds
-> ~20% of company value per year after your company reach 1 500 000 pounds
-> cash from tax is assign for creation of new industries
Now you need to make progress in game to earn more money. Tax cause that you stop earning money at some level until you don't increase your company value.
Here is another one:
Vehicle Repair Cost
It case that we pay for each breakdown when vehicle is repaired in depot. If vehicle didn't broke since last visit in depot we don't pay. Cost of repair for each breakdown is 1/1024 vehicle value.
So simple patches but can make game a bit difficult and challenging. I'm open for any ideas to improve those patches.
I'm using them in my server pack with few other patches - for full list and download click here.