Why is Spartan-3 more expensive than Cyclone?

Possibly because you are comparing two very different sized parts in two very different packages.

The EP1C6 is in a 240 pin QFP (read lower cost package) with about 6000 LEs. The XC3S1000 is a newer technology which should be cheaper, but you picked a BGA package (which tends to cost more than QFPs) and a

I suggest that you compare the Cyclone II and pick an equivalent part. How about the EP2C20F256C8 with 18,752 LCs in the same 256 pin BGA at $42.70...? Now it is only a bit cheaper.

the price difference would be mainly due to the difference in logic density. the Xilinx XC3S1000 has more LUTs (4-input Look Up Tables) than the Altera EP1C6. if price is a concern, you might consider Lattice's low cost FPGA, the LatticeEC

Vendor Device LUTs 1pc. Price

-------- ----------- --------- ---------- Xilinx XC3S1000 15K ~$50.00 Altera EP1C6 6K ~$19.00 Lattice LFEC6 6K ~$18.00 Lattice LFEC15 15K ~$36.00

What about the LFE2 parts? I thought they were starting to ship now and even cheaper.

the original question referred to distributors such as Digikey, so at the 6K and 15K LUT densities, the 130nm LatticeEC is the best fit for devices that are available from Mouser and other specialized distributors off the shelf.

you're right, the 90nm LatticeECP2 device is now sampling and is lower priced, however the smaller densities (6K-15KLUT) of the LatticeECP2 are not currently available through distributors such as Mouser.

... while the Cyclone II also has 4 inputs per LUT AFAIR