Like others have said, most of the price comes from the time and effort that the artisan put into them. Cheaper glass is made with a mold and mas produced so even thought the glass may be the same type, it does not have the same love.
It really comes down to looks when you get right down to it though, your orifice of choice won't care about the price, only how good it feels. So it ends up being your eyes that decide if it is worth the price.
FYI, Taken from Wikipedia "Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915" " Corning sold off its Consumer Products division in 1998 as World Kitchen but retained the Pyrex brand name, licensing it to World Kitchen and other companies that produce Pyrex-branded cookware"
So just so everyone knows, chances are your "Pyrex" toy is not Pyrex. I am pretty sure that World kitchen does not make dildos. When I did my first drop test, Pipedream corrected me and stated that their glass is Borosilicate and not Pyrex. I also informed EF about this, but I have not seen any change as of yet.