Supermicro 36 bay 4U storage chassis - $249 + $39 shipping

Looks like you might need to modify the backplane depending on the motherboard used. Apparently some Supermicro models work natively.

$249.00 + $39.00 shipping for barebones

https://rover.ebay.com/rover/1/711-53200-19255-0/1?mpre=https%3A%2F%2Fwww.ebay.com%2Fitm%2FSupermicro-36-bay-4U-Server-Storage-Chassis-Extended-ATX-Ethernet-Freenas%2F202805514541%3Fhash%3Ditem2f3826912d%3Ag%3A-HEAAOSwf7dZf0ej&campid=5338535236&toolid=20008

$275.00 + $69.00 shipping for…

  • SuperMicro X8DT6 (dual 1366 w/ LSI SAS 2008)
  • Dual Xeon E5603
  • 24GB DDR3 ECC REG

https://rover.ebay.com/rover/1/711-53200-19255-0/1?mpre=https%3A%2F%2Fwww.ebay.com%2Fitm%2FSupermicro-36-bay-4U-Server-x8dt6-a-is018-2x-E5603-24Gb-Ram-Ethernet-Freenas%2F193060370290%3F_trkparms%3Daid%3D1110012%26algo%3DSPLICE.SOIPOST%26ao%3D1%26asc%3D20200420083544%26meid%3D48ce48308c844d5b9c6021fc479c8e78%26pid%3D100008%26rk%3D3%26rkt%3D12%26sd%3D202805514541%26itm%3D193060370290%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DPromotedSellersOtherItemsV2%26brand%3DSupermicro%26_trksid%3Dp2047675.c100008.m2219&campid=5338535236&toolid=20008