everything is design for a purpose ... those skimpy tie string
ones are meant for lazing on the sand ( sun tanning) with minimal
movements. I'm sure many girls have enough sense to not wear the
skimpy tie string ones for virgorous activities such as wake
boarding ... else when you do your turns or simply splashes into
the water , ofcourse everything spills out. Then again, there maybe
some that do so just to attract the guys .....
as to why they cost so much .... well designer lingerie don't come
cheap either .... it's just plainly demand, supply and how willing
you are to pay for the brand/design.