Are there enough skulls in the game to buy all upgrades?

Question

Are there enough skulls in the game to buy all upgrades? Each level seems to offer only up to five; with a new trap given every level and upgrades costing more than five skulls, it seems like you can never get enough skulls.

Or can you?

Answer 1

Orcs Must Die! has at its core has 19 traps with upgrade costs as follows:

#   Trap            Skulls to Upgrade
1.  Spike Trap        8
2.  Tar Trap          8
3.  Boom Barrel      10
4.  Barricade        12
5.  Spring Trap      12
6.  Steam Trap       12
7.  Decoy            10
8.  Brimstone        12
9.  Spore Mushrooms  16
10. Coinforge        18
11. Arrow Wall        8
12. Wall Blades      14
13. Push Trap        10
14. Grinder          16
15. Pounder          14
16. Swinging Mace    16
17. Autobalista      16
18. Archer Guardian  14
19. Paladin Guardian 14

Total               228

There are 24 levels in OMD! with 5 skulls for warmage and 5 more skulls for Nightmare so 240 skulls. Yes, in the base game of Orcs Must Die!, there are enough skulls to buy all upgrades.

The Artifacts of Power DLC adds:

#   Trap            Skulls to Upgrade
20. Shock Zapper     16
21. Floor Scorcher   16

New Total           260

With the Artifacts of Power DLC, as 260>240, no, in Orcs Must Die! with the Artifacts of Power DLC alone, there are not enough skulls to buy all upgrades.

The Lost Adventures DLC adds:

#   Trap            Skulls to Upgrade
22. Mana Well        18

New Total           278

The Lost adventures also adds 5 more levels so 50 more skulls, meaning 290 total skulls. So, yes, in Orcs Must Die! with the Lost Adventures DLC, there are enough skulls to buy all upgrades with or without the Artifacts of Power DLC.

Answer 2

It is possible, but you have to essentially beat the game twice to do it. You have to play through once on War Mage, and then again on Nightmare.

As further backup, a quote from the developer:

To upgrade every trap, you have to five-skull every War Mage and every Nightmare level. You can get around half of them upgraded by the end of the War Mage campaign, so pick the ones you'll use the most.

I haven't played any of the DLC, though, so if you are including that it's possible that this answer changes depending on how many new traps versus new levels are introduced.