How about $17.50? If you know for sure that you can load some maps into the card, and others into another card, and switch them out mid-stream, I’ll pony up the $20.
Whoops! I should have checked back here sooner. Yes, you can swap chips with different maps on them. One of the popular eBay sell points of the chips is that often a seller will preload a map on it for someone buying the chip but not having mapsource. I sold a 64meg chip that way when I bought my Garmin V and didn’t need the big chip in the eMap anymore.