Looking for an expensive gravel bike? How about something more robust with much wider tires than your fast carbon or ti CX/Gravel steed?
A lot of larger towns and most cities now have some sort of bike Co-Op or Conservancy.
This is a shameless plug for these non-profits.
These typically are non-profits and to pay the rent and keep the lights on they sell used bikes and parts. These are great places to find INEXPENSIVE stuff, but best of all every co-op I've been to has mechanic programs where one can volunteer and earn bikes. Co-Ops are supporting the bike community, hopefully you have one near you.
The Fort Collins Bike Co-Op, like similar operations in Boulder and Denver Colorado, have bins and bins of used parts. Inventory changes quickly so it may take a few trips and some patience to find that more obscure stuff.
Currently I'm working on the restoration a 80's Miyata 1000. A bike Sheldon Brown praises as one of the best touring bikes. It's an excellent platform to build into a steel gravel grinder - similar to the Surly Long Haul Trucker and Soma's Saga. It's well used with lots of scuff marks and a bit of rust but it has lots of life and depending on the parts for the final build it'll sell for a bit over $200.
I've also built up several 26" monster cross (aka gravel grinders) bikes from high end rigid steel mountain bikes. Replace the flat bars with drops and appropriate brake levers and you're almost there. Shifters are a bit more challenging as some of the thumb shifters can be used on drop bars but most need to be replaced with bar-end shifters or another alternative. In the flats, my 26" Frankenbikes keep up with cross bikes just fine. When the going gets soft the 26x2.3" tires really get going. BUT at 27 to 30 pounds these bikes are more effort in the hills. Fortunately they have wide gearing thanks to the triple crankset so there's never a problem getting to the top - it's just a question of how long.
