I remember it as one of the earliest big boxes, like the Charlie Parker on Verve, so for me it was too expensive at the time (early Nineties when I was a student). I passed on the Parker for the same reason. The first big box I got was probably Billie Holiday on Verve. It felt like a big outlay -- but it was worth it.
That Kirk Mercury box was the very first CD box I ever bought - hadn't even heard of Mosaic back then. It was over $100 Cdn at the time, which felt like a King's Ransom (but one you just had to pay). The Clifford Brown box was the next..