A very expensive modern European sword will likely have been hand crafted with great consideration to maintain consistency in the blade. There would be no soft spots or flaws, it would be balanced very well, feel extra comfortable and so on. But to answer your question bluntly, if you went back in time to say, oh I dunno, the 1200's, you would be better off with even the least expensive battle ready swords offered today. In those times, many swords were hammered out in haste and issued to soldiers. Prone to corrosion and chipping, those swords, while fully capable of enduring battle, were still not really all that wonderful when compared to the pieces we see today. Only a select few swords of that period would have been painstakingly crafted with incredible attention to detail and perfection, and these swords would normally only be seen in the possession of wealthy folks, nobility or royalty. Unlikely would such a sword ever be used in combat either, nor would it be left exposed to the elements. So effectively, it wouldn't matter which sowrd you brought back in time with you, the Kingmaker or the Henry, they would both be leaps and bounds beyond the quality of true medieval swords.
Modern science and technology has allowed for incredible advancements in crafting metal blades. While the differences are subtle between a thousand dollar sword and a $250 sword, as mentioned above, they are indeed there. But, I'd be more willing to bang up a $250 sword than a $1000 sword. i mean, you can go through 4 cheaper ones for the price of one expensive sword. If I had a $1500 sword, I certainly wouldn't abuse it in any way... unless I was some rich weirdo who had nothing better to do with my money, lol.
Yes, there were low-quality implements and there were less "controls" regarding contamination of steel, but I highly doubt that you can say that the less expensive examples of swords today would be better than a similarly priced one going back some 500-1000 years. Similar problems plague these weapons SIMPLY because quality costs money, and the less time and effort and care put into a weapon, the cheaper it is - I highly doubt CPM metallurgy is used in China or India-made budget cutlery

. Also, if a smithery produced many subpar weapons that had various structural flaws, such as small tangs welded to rat-tail threads, steel that tended to fracture, chip, or bend easily, badly balanced blades, etc that smithery would probably not get much more business, despite the relative difficulty in transporting a large amount of goods during those times due to technology and political limitations.
For one, those swords, spears, and such, WERE actually used and users could probably provide decent feedback to any smiths they might purchase from (they might even be neighbors - see below). Many farmers/hunters/militia used simple weapons based off of implements they would use at home, including spears, bows, axes, and clubs. I would be very much surprised if the majority of the "peasant-soldiers" were even provided weapons by their feudal lord or whomever would be in charge of such. More than likely, these weapons were simply tools that they used at home - see the messer for a good example.
Finally, in swords, you get what you pay for in general, with diminishing returns as you reach about 1500 dollars, where it becomes more about the fit and finish, rather than necessarily the functional quality of the sword that becomes more evident as price rises. For the money (~400-700 USD), I don't think you can beat a sword from Angus Trim. That said, Albion, Arms&Armor, and several custom makers make fantastic weapons at a variety of price levels - but again, you get what you pay for. Distal taper, balance, edge consistency, blade geometry, harmonic balance, and heat-treat all come into play, and time and effort at every step adds to the price. Also, for the below US$300 crowd, there is Kris Cutlery and some newer Gen2 swords (though they tend to be heavier and more forward-balanced than they "should" be in some cases).
Simply see the thread below:
Good hand-and-half? for some examples.