Yes, but many hobby shops have half-pint bottles of the Testors thinner, and if you buy those, thinner is not a major hobby expense. Be very careful of what thinner you buy in a hardware store for thinning enamel. Some of that stuff, sold as generic "paint thinner", is really cruddy. It has a milky appearance, and has a lot of dissolved solids in it.
I only buy stuff specifically marked as turpentine or mineral spirits.