Alex,
If you look at the top of the page, on the banner there's a section marked "nihonto info," under that heading there is a "links" section which includes links to legitimate dealers in Japanese swords. You can use that to begin to get a feel for the market and what you can get for your money, but there won't be any Masamune blades by "the" Masamune on any of them. You can also check out the sales section on this forum as members are often selling blades and there's some nice pictures to look at.
Please avoid buying on Ebay or the Japanese auction sites (probably best to avoid buying at all right now as you're shark bait; sorry): there are a lot of blades tricked out to look like something way more attractive than they really are like the second one you've posted above. I don't know where you get Masamune from there, it looks like a shinto blade that has been doctored to appear to be by Sekishu Naotsuna, I think. So in effect, you've been deceived twice in one go and you've barely got started. The new looking kinpun (gold) attributions on them is a big giveaway as if you check between blades, the style of writing is identical so someone has bought a comic with a free Japanese swordsmith kanji stencil set in it and they're really making use of it.
Essentially if it's a blade claimed to be by a big name smith and it doesn't have modern NBTHK or NTHK papers, in most cases it can be discounted as a fraudulent attempt to deceive. Even if they do, you need to be sure that the papers are to the smith the buyer is claiming it to be as the names can relate to mulitiple generations of smiths with the same name, not all of which are well regarded or smiths from a different province with the same name who again may be inferior.
A long-winded way of saying you need to know more before parting with any money.