Hi,
I couldn't find Building Upgrade Costs information, I believe it might not exist. Why Plarium makes it so 'confidential'? It could be quite useful in planning.

Let's try to show this costs.

If you want, please add the costs you know in comments, let's focused on the one where upgrade chips are needed. 
Providing the build time isn't needed as the players might have different builing speed modificators.

proposed format:    bulding name L:level_after_upgrade; UC:Upgrade chips; [+extras].

Bank L:21; UC:75.

Bank L:22; UC:165.

Bank L:25. UC:455

Breed Reactor L:6; UC:550

Bunker L:21; UC:150.

Bunker L:22; UC:350.

Bunker L:23; UC:600.

Bunker L:25; UC:2000

Emabassy L:21; UC:200

Financial Corporation L:6; UC:550.

Financial Corporation L:7; UC:1800.

Hospital L:14; UC:800

Industrial Syndicate L:7; UC:400.

Ore Rafinery L:6; UC:550.

Research Center L:21; UC:600.

Research Center L:22. UC:1500

Senate L:21; UC:600; +resource & command buildings on L:20, hospital L:13, incubator L:1.

Titanium Mine L:21. UC:120

Titanium Mine L:25. UC:620 (fun fact: takes 22 days to build with maxed senate and build speed tech) 

Trade Center L:21. UC: 240

Trade Center L:23. UC: 650

Trade Gateway L21; UC:180

Uranium Mine. L:22. UC:200

Uranium Mine L:23. UC:300  

Vault L:21, UC:180

Vault L:22, UC:260

Warehouse L21; UC:75

P.S.

Thanks Commanders for responses! To have everything in one place I will periodically copy here your findings. Good Luck and Good Hunting!