With After the Fall I spent a fair amount of time making the early prototypes decent looking and playable, but they were not very expensive or high quality. I used printable business cards for the cards and printed paper for the mats. The counters were Smarties!
The game progressed very rapidly, changing with each play test, sometimes drastically. I did spend time on the graphic design as the game changed, but the components themselves were disposable and felt that way--easy to replace. Usually each play would have several (if not all) new components.
To some extent Archon Arena went through a similar lifecycle. Early prototypes were business cards. Often I'd simply write changes on them rather than reprint the cards. After ordering real cards, the gameplay has changed much more slowly. The second set of cards basically just reflected a redesign of the layout, and very little has changed since then.
Maybe it's just the natural progression of game design. As the game gets more concrete, the prototypes get better, therefore, there are fewer and fewer changes. The key then is to time the quality of prototyping properly to coincide with the level of completion of the game.
With I Thought There'd Be Zombies! I feel like perhaps the good prototype came too early. The game is fun as is and certainly playable, but I continue to second guess basic elements of it. It'd be a lot easier, mentally, to make drastic changes if it didn't involve throwing out a $10 game board and/or $20 worth of cards.
It'd be great to hear from anyone else who's had experience with this phenomenon. Is it just me, or can high quality early prototypes virtually kill a game?