Most mass-produced guitars cost 10% (Yamaha) to 20% (Gibson) more left-handed. Manufacturers who make no surcharge (Taylor, Martin) tend to make one-offs to order, which means there are never any available to try. Shops never stock more than entry-level lefty instruments. This is the general rule, but there are exceptions.

Seagull guitars are about 5% more left-handed, and availability is good (though mine was shipped to special order). When I spoke to Fylde guitars, they offered to restring R/H examples of their entire range for me to try if I visited the factory. Regent Guitars in Leamington Spa (England) have a decent lefty stock and will try to obtain demo. guitars from other shops for you to try without obligation. They, too, offered to restring an instrument to get an idea of what it plays like.

Nobody makes left-handed guitar cases; you are expected to carry it in the "wrong" hand.

I do, however, play a right-handed mandolin upside down - the tuning is the same as the bottom four strings of a guitar.