For my purposes, I think that a good scanner plus a vector graphics program is just as good as a drawing tablet, if not a better deal for the money, because I can use a tracing algorithm in Illustrator or Inkscape (like potrace) to convert a pen drawing into vectors, and thence back into rasters. To that end, I'm sort of basing this on this question.
But I also want to define what I mean by 'good.' Good in this case means something like the iPod Nano 1g. I don't buy Apple products in general, but this one works well with Linux (hence any other OS), has really high quality parts (has survived sub-zero temperatures, being dropped multiple times, being left on all the time, etc.), and still does what it's supposed to do after having logged thousands of miles of travels around the world.
A scanner with those qualities would either be a good thing to buy used or a good investment if bought new, but I wouldn't be able to spend more than £100 or €100.