I like the idea quite a bit. I've discovered that it helps me stay on track and keep going to have something tangible around, as you said, something I can touch and look at to remind me of how far I've come. Not just an abstract idea or number (which is still somewhat unfathomable to me). It kind of makes this whole thing "more real".
(Plus, this money jar will come in handy when you need to update your wardrobe
)