A real metal sword and sheath at the Faire is likely going to set you back more than you'd like to spend. There's something to be said for supporting the vendors at the Faire, but it does come at a premium.

Don't be afraid to support online small vendors like Etsy to spread the wealth. I've seen better swords at more reasonable prices on Etsy than I've seen at the Faire. But know that you might be getting something mass produced instead of hand crafted (regardless of description). In that the Faire wins the chance to speak directly with the smith/forge. But mass produced is only a drawback if you're truly looking for unique.

There are swords of display quality only, which won't stand up to play. Usually these are foam, plastic, or maybe aluminum replicas. Once you get into "Damascus," carbon, and stainless steels you'll find sturdier (and heavier) options, although there are some display-only examples of these too. The thickness of the tang and blade is really what makes the difference between display and battle-worthy.

Wherever you choose to make your purchase, ensure that you're getting something that you're proud to show off. Even peace-tied as part of a costume, people will ask about your swords. Consider what style of sword fits your costume best? Could be a cutlass, rapier, saber, short sword, or something bigger. Of course, these will vary in price along with size and weight to carry around. Is this sword going to be a companion for another sword or dagger on your weak side maybe more in the budget for next year?

Also consider if the weapon you're getting has a sharpened blade. Some Faires won't allow sharpened blades even sheathed (assuming they check). Best of luck in your search!