All systems have a PII-350 CPU, and 128MB RAM.
The basic configuration is as follows:

It should be noted that this falls short of being an apples-to-apples comparison, owing mostly due to the fact that SCSI opens up more configuration possibilities.  For example, LHS use a faster but smaller hard drive, some of the places use small hard drives ( a  9G hard drive will usually cost an extra $250 or so ). The onboard controllers are usually cheaper ( they add at most $200 to the price of the motherboard )  .  Warranties shouldn't be taken for granted: a machine with a 2 year warranty is worth about $100 more than the same machine with a one year warranty.  Actually, I find it hard to pick any vendor as offering the "best price" . However, it's interesting to note that some of the shops usually considered "expensive" don't look so bad when you look at SCSI systems.

The different vendors  include  different "value-adds". For example, ASL ship their machines with Xi accelerated X-servers, and Penguin ship with a boxed set plus extra docs. The value adds make for an "error" of about +-$50 in the prices.

Also, it's worth noting that the different vendors vary in what they do in the way of burn-in, testing, and configuration options for the user. Vendors like VAResearch, LHS, and Penguin do some "burn in" on their systems prior to shipping.
Vendor Model Motherboard SCSI controller HD Video Modem ZIP ? Warranty Price
Advanced Systems Labs PII SCSI ASUS P2B-S Onboard Adaptec AIC 7890 U2 4.5G LVD IBM Matrox External SCSI 1 year $1878
The Computer Gallery custom ASUS P2B Adaptec AHA 2940 U2W 9.1 G IBM Matrox External IDE ? $2035
Dell Precision WS 410  (?) onboard U2W of some kind 9.1G U2W Diamond Permida 2 8MB AGP No No 3 year $2415
Linux Hardware Solutions PS350WS100 ASUS P2B Intraserver 3140U 4.5G LVD Seagate Cheetah  Diamond or Matrox None None ? $2361
Penguin Computing PII SCSI Supermicro P6SBU Onboard Adaptec AIC 7890 U2  9GB Quantum Viking II Matrox External SCSI 2 years $2213
SWT Pentium II-350 
ASUS P2B Adaptec AHA2940 U2W 9G IBM Ultrastar Diamond or Matrox External SCSI 2 years $2382
TCU-inc Custom ASUS P2B-F Adaptec AHA2940 U2W 9.1G Quantum  Diamond or Matrox External SCSI 1 year /
3 years
VAResearch VARstation 28 Intel SE440BX Symbios 8951U 9.1G Quantum Atlas Matrox Internal None 1 year $2305