Managing the resources of a studio requires making decisions like this all the time, and you have to find a way to make the decisions more transparent to yourself. Thinking of them in two parts helps: 1) What is the equivalent money value of the gear, and 2) Which pieces am I going to use most in my work?
I used to own an akg "the tube" mic. It was a nasty-sounding piece of shit. I was thrilled to get $1000 in trade for it a few years ago, having not used it on a session in half-a-decade. The AKG C12VR, despite hype to the contrary, was essentially the same mic with a different (still not great) capsule. I have used them and been unimpressed since. If I had bought one for $5000 or whatever they were going for when they were released, I would have felt robbed.
The ASB is expensive, sure, but I don't know of another compressor on earth that can do exactly what it does best, which is truly inoffensive vocal compression.
The secondhand market on those two mics has spoken, and together they're worth just over three grand, maybe a little more if you find a sucker. You are essentially being offered an ASB for three grand, and that's a fair price.
Since the swap is a fair one in terms of monetary value, you need to decide which you would use more, the compressor or the two mics, and let that be the decider. If you have a piece of equipment you do not use in your studio, it may as well be a brick. If someone said you could trade a brick for $3000, you'd probably do it. Keep and acquire the things you'll use, shift the things you won't.