Filet Mignon is a very tasty cut of meat but yes it can be expensive.
The cheapest I've seen Fillet Mignon was for $14.00 per lb and the highest I've seen it at some stores is $20.00 per lb.
It's worth it though if you can afford the cost of the Fillet Mignon as it makes very tasty stews and is very tasty by itself as well.
If I could afford Fillet Mignon more I'd buy it more often.