S.
What I did for my daughters preschool teachers is a summer planter. I went to WalMart and got a sandbucket ($1), we picked out about three 4 packs of plants ($1.25 each) and a container of foamy stickers in flowers and butterflies ($4.95) I wrote "happy summer" on the bucket in marker, had my daughter write her name on the bucket and had her decorate it with the foamy stickers. We then planted the flowers in the bucket. It was cute, something that each of the teachers loved and can put on their patio/deck/front step for summer and it was all basically made by her. I think my total cost for doing 4 of them was around $20. Being a teacher myself, I would rather have something that was meaningful and thoughtful instead of another coffee mug or even a gift card.
It's not about the cost but about the appreciation. I do also write a personal note to the teachers thanking them for all the hard work that they do for our kids.
Good luck!
S.