They cost 100 gold normal wards cost 70 Normal wards are stealthed and take 3 hits pinks aren't and take 5
whats thep oint of them I thought the whole point of wards was vision and surprise but pinks everyone knows where they are and even if u kill a ward you only save 5 gold until they kill urs then they save 30 gold cuz they know where it is
Pink Wards do not expire. You can put one up and have it last 10+ minutes without being found. 100 gold for 10+ minutes of vision is well worth the cost. Even if it only lasts 4 minutes before being found, it paid for itself. Pink wards placed in the right spots can also show you where enemy stealth wards are. Pink Wards also warn you when a stealthed enemy is near. Think Teemo, Rengar, Kha'zix, Twitch.
thank you everyone so much for the replies
I had no dea they didn't expire
nor did I think of their utility against stealth chmaps I am a shmae
The whole point of pink wards are for map vision control in heavily warded areas like dragon and baron. When you buy pink wards, you want to place them in areas near you that you can defend if the enemy tries to kill it. The pink ward lasts forever if the enemy never touches it and serves the purpose of providing you better vision control of an area when your scanner trinkets are on cooldown.
I find pink wards to be super useful especially when dealing with champs that can be invisible, like 
or when champs like 
uses his ult. During team fights I always like to pop the pink ward somewhere in the middle of the fight so that these champs doesn't go unnoticed.
Don't forget that you have the option of upgrading yellow trinket into a pink ward dropper (still can only have 1 on the map though, so I never actually find it to be worth it)
