If you are near a larger city, I would look into colocation hosting. Buy the hardware up front, and get some big disks. RAID or ZFS for redundancy.
My rough guess places it between FPGA implementations and GPU rigs. The only problem is producing the code. FPGAs and (probably) these are harder to manage and set up but will yield better results per dollar and Watt.
If you are near a larger city, I would look into colocation hosting. Buy the hardware up front, and get some big disks. RAID or ZFS for redundancy.
My rough guess places it between FPGA implementations and GPU rigs. The only problem is producing the code. FPGAs and (probably) these are harder to manage and set up but will yield better results per dollar and Watt.