705s can be had for $350 or so. another option, if you have a GPS-enabled cellphone, is to go for a 305 (doesn't have mapping, but can be had for $150 or less these days).

I bought an edge 305, used it for a month, and traded it in on a 705. not sure whether it was worth the extra $200, but I am using free maps that work great, so at least I didn't have to pay even more