[walrus01]

What I've noticed is that if you want to build a dedicated indoor trainer bike from used parts, there definitely is some good opportunity now to pick up previous generation stuff for cheap.

As serious road frame design is moving to disc brake and thru axle, something like a 12 year old all aluminum Cannondale or specialized road frame and fork set for QR skewers and 130mm rear should be pretty cheap. Then add basic all aluminum components for stem, bars, seatpost, etc.

I'd still expect to spend $125-200 on the saddle if I want exactly the same model to match my actual on-road bikes.

[inopinatus]

For this build I acquired (from eBay) a bargain-basement second-hand test saddle of the same model I use in competition. Well, it was the alloy-rail version rather than the carbon-rail version, but otherwise identical in form. My butt was happy with it, which is what matters.

Can confirm it was still the single most expensive component of the whole bike build, more than the frame, wheels, or groupset even.

Test saddles aren't supposed to be sold to the public; I believe it was a liquidation sale.