what's a fair price for this pair of K-tubes?

[freddi]

(don't say "50 cents". 😀). - got to sell everything I can to pay taxes or will lose my income completely and forever. Its effectively 1/10 of its best years.

they're based on one tube seen in Karlson's "X15" system but longer at 9 inches. OD = 2", ID ~1.875" and a parabolic function slot.

 

[Lojzek]

Ask someone at a metal shop what would have cost to manufacture such, then you will decide.

 

[KatieandDad]

Probably not a lot as they would be easy enough to fabricate.