S.B. Dealers will charge what the traffic will bear, the model 28 currently list in the "Blue Book of Gun Values" for $270.00 in 100% condition. I just checked Auctionarms.com, there is one there for $250. complete with holster and speed loaders. There is also one on GunBrokers.com for $600. but it is an unfired, 8 inch barrel model. I worked a gun show two weeks ago here in Texas, and sold one for $175. it was not a pristine gun, but still had a lot of life left in it. As for not making the gun anymore determining the price, this gun is similar, in some respects, to the thousands of Milsurp guns on the market today. The gun was/is not a highly desirable piece, there is little or no historical value, and the move to automatic pistols by most people, Could it be the crazy gun laws of Illinois has driven the prices up in that area? I can think of no other reason that a sane person would ask, or pay $400 for a model 28.
The "Blue Book of Gun Values" is pretty much the standard for gun dealers throughout the USA as is the "NADA Book" for automobile dealers. I would think someone attempting to sell a 28 for $400. is either "smoking something," or a fly-by-night dealer who is out to take advantage of someone. My advice at this point is, if barber truly wants a model 28, and does not have to have it TODAY, then monitor the two sites listed above, and make a purchase from someone there. All one has to do is find a licensed dealer that will do the transfer for them, have the dealer provide them with a copy of their FFL and they can make the deal, have the gun shipped to the dealer, and pay the dealer a small fee for the transfer (my dealer charges me $10. but as I said above, I help him at gun shows0. The sites will even provide a list of dealers that will make the transfers, and the fee to do it.
Keep in mind, when you buy on-line, look at the sellers rating, if they have a bunch of bad ratings avoid buying from them. Most of the people that list on these sites are honorable dealers, and will be fair with you. They will also accept a return if you are not satisfied with the firearm.