Limits are 15-25$ before shipping. If you spend slightly more than the max that's fine. If you spend slightly less than the min... well I would hope its at least close to the min.
There's no way to judge what gifts are worth in a secret Santa. The price range that is set is merely a guideline. There are deals and sales everywhere and perhaps someone has some valuable stuff laying around like diodes, hosts, and so on. Hell, it doesn't even have to be laser related! So no worries if your gift was "slightly" more. Who am I to say? I can't control what you guys buy for each other!
Just be fair in what you send. Example, a coffee mug would not be an excellent gift as I'm sure we all have tons of these.