So assuming those are correct, this makes the the Mega Gargants $206 CAD (the currency ill use for the rest of this), and the box of 2 Mancrushers $129. Lets round these off to $200 and $130 respectively.
So with our known 3 of building a 2k army, here is what I came up with.
1 mega, 9 crushers: Total cost is $850/495pound, while leaving 1 mancrusher at home.
2 mega, 6 crushers: Total cost is $790/445pound, nothing left over
3 mega, 3 crushers: Total cost is $860/510pound, yet another mancrusher left out.
I expected this to be roughly the cost, admittedly more than I would want, but compared to other armies, this is not all that bad. Surprisingly just buy 3 mega's is actually the most expensive route to 2k. Who would have thought that.