$4K starting for a used rifle and used optic. It does look like an older USO, so it might be okay (I'm more of a fan of the CA made ones). At best, it is a used rifle still that might pull $1,500 - 2,000, and a used optic that would probably fetch the same at best. That would put it closer to the $3K range for me. $4K requires the buyer to have a hard-on for both the Seekins and the USO... and I'm not a fan of a 20" long (exaggeration) 5-25x on an 18", .308.
I've purchased some used higher-end guns that were used on GB before. My personal rule is to bid no more than 2/3 the cost of new. It means that I pass up a lot of cool-looking items, but I'm not paying new prices for used equipment. Others might see differently.
Remember that you are still taking a risk on buying someone else's problem.