Thinking about the current storage capacity of my card index collection, I made a back-of-the-index-card calculation:
172,000 index cards * 150 words / card [average maximum, using front only] * 1,200 bytes / 150 words [rough average with Unicode encoding] * 1 kb / 1024 bytes * 1MB/1024 kb = approximately 200 MB of text storage

Having it well organized and indexed… Priceless.