I see the problem you note. Since JSB is the lowestest end SRX300 sold why is there such a big price difference between those two postings at CDW. And the lower price one does not mention JSB but just the model number.
In my experience Juniper only sells devices without any license or production use privilege for labs, hot hardware spare and non production demo/training specifically labeled NFR (not for resale) and approves these through partners per deal.
So I think this first lower price listing was some kind of sale posted by CDW and will also be a JSB device.
Maybe a partner/reseller can chime in on the processes here.