In PC Magazine from July 1988 there is an advert for a 15MHz XT for $575 with an optional 30MB Segate ST238 5.25" scsi hard drive inside for an extra $295 [0]
The price hasn't dropped much since, it's now $206 for the drive [1]
[0] https://archive.org/details/PC-Mag-1988-07-01/page/22/mode/2...
[1] https://www.amazon.com/ST238R-Seagate-3600RPM-Internal-Drive...