When we were there a couple months ago, it was $15 for one, $25 for two.
A wheel on our double stroller broke while we were there, so we rented two single strollers (they do not rent double strollers...frustrating) on our last day. Oh my lord, the rental strollers were HORRIBLE. Well, I suppose one might like them if they want to be awed at the miracle of modern science that a piece of equipment can actually possess a brain of its own. But if you want a stroller that can maneuvers well and does not destroy your wrists by the end of the day, then those DL strollers are not going to be a hit. Perhaps we coincidentally got the only two strollers in the park that didn't work, but somehow I doubt it.