The only time I have even seen a pair for sale was on that auction site about a year or so ago.
If I remember correctly, they went a little north of $1200 for the pair. Can't seem to find them in "completed sales" right now using my smart phone - maybe on a real computer I could.
According to Blue Shadow (one of the DCM gurus around here), TW^2 were produced from 1982-84 and sold for $2,197/pr. Guessing by known serial numbers, probably < 500 pairs were manufactured.