I can't believe it... (part 1)

So I had just figured out that, financially, we have exactly enough money to make it through the summer. That means we've spent $10K more than the initial bid on the addition and all $5K "extra" beyond the cost of the addition. So what happened yesterday? Well, we'd been seeing a few ants in the kitchen. The added weight of the addition opened up a crack near the door and I saw ants retreating into that crack:

However, when we had G's family over for Memorial Day weekend, his sister and brother-in-law saw one of the ants and said "you have carpenter ants." (they have had a lot of experience with them, as two of their trees have been infested) G's sister told us to look at trees nearby--especially if they have branches hanging over the roof. Well, the one remaining tree in the front of the house has this at it's base:
and when I looked up, there was a string of carpenter ants going into this fork in the tree:
This is the birch tree that we've been treating for birch borers, and cutting dead branches out of for the last two years. I guess Carpenter ants like the soft, dead wood, so they've taken up residence there. The ones we've seen in the house are probably scouts, sent out to find a place to set up a NEW nest. UGH!

Estimates for treatment range from $50 (spray the tree once) to $350 (spray all the trees on our lot and the house and guarantee it to be free of ants for 6 months).

Bye, bye money...