I don't think anyone is trying to give you a hard time, it's just a lot to ask of someone who doesn't know you. This sort of arrangement are often used for fraud, so people are naturally skeptical. Also, given that you're in Russia, there are export restrictions to consider, which are a big pain in the US. If it turns out that the oscilloscope falls into a restricted export category that can turn bad for a person who helps you (fines and worse are possible, even if not super likely). This is probably why the seller will not ship to a freight forwarder or accept payment from international accounts. If they deal with a lot of test equipment, they almost certainly handle export-controlled items, even if your scope is not one of them, and doing the compliance work probably isn't worth it to them for selling used gear.