I just bought an X9SCL (non F) with I/O shield for 60 USD including shipping on eBay last week. That one was listed for several weeks before I bought it. There are plenty of them listed for more. The versions with IPMI do demand a premium.
I love them as low power servers as long as you can live with the limitations. It does require unbuffered ecc memory that is more expensive than either regular DDR3 or registered memory. It only accepts celeron, pentiums, some i3's and xeons processors. It won't take an i5 or an i7. It has a limited number of PCI slots. The basher box I installed the one I just bought is full with a 10GBE NIC and a SAS card in the two x8 slots and an eSATA card in the x4 in x8 slot. I am using the Celeron I had in the motherboard it is replacing along with some 1G unbuffered ECC DDR3 sticks I had in the parts bin. The X9SCM is a nice choice if you can use the extra x4 in x8 slot but goes for a lot more money.
The other limitation, which I consider the most serious, is it is not ESXi certified and does have a few compatibility issues. I am in the process of moving my public facing VMs from one to a dell R210-ii. This is only an issue if you plan on running ESXi and care about it filling your log file and occasionally crashing one of your VMs.
Oh, and it it has a supermicro proprietary front panel connector. This is not a problem in a supermicro chassis or if your chassis has the individual breakouts. Mine, unfortunately, has a 9pin (2x4) connector and I can't for the life of me find a 9 pin "standard" to 20 pin "supermicro" adapter cable. There are oodles of people selling cables to put non-supermicro boards in supermicro chassis. I got it to work by shorting the "power on" pins with a knife until I figured out I can turn the 9 pin cable sideways to get the power on button connected to the proper pins. It is a pain but works and kinda off topic.