- Edited
The AXE XCaliber Tour X shafts are about 30% less than the Aerotech shafts, and they are every bit as good (actually better, in my opinion). Still a pricey shaft at $30/ea, but they'll save you over $100 compared to a set of Steelfibers. https://www.golfworks.com/axe-xcaliber-tour-x-graphite-iron-shafts/p/AS0036/
If you're looking for something a little cheaper, check out the Matrix Kujoh 85 for $15/ea from Diamond Tour. Heck of a nice shaft with a mid kickpoint and medium ball flight, 2.8° torque, and weighing between 76-84g depending on the flex. According to the specs, they should play fairly similar to your Penley Stealth 80 shafts which are 85g, mid-kick, 2.9° torque. http://www.diamondtour.com/golf-components/club-shafts/matrix-golf-shafts/matrix-kujoh-85-iron-shaft.html.
Also, the Powerflex FW 501 shafts from Hireko are exceptional shafts for the price ($10/ea). They're on the heavier side of things at 86g and will be slightly lower launching than the Kujoh 85. http://www.hirekogolf.com/golf-components/golf-shafts/graphite-shafts/powerflex-fw-501-graphite-shafts.html