Babe Ruth has been dead for over 20 years. In the past 5 years, they have printed over 200 different cards from 7 different companies. None of them is worth anything save 1. And when I say 1, I mean there was not one print run, but 1 actual card. It is a Babe Ruth Cut signature card, only 1 made. The packs that it was in sold for $100 each and the card is worth over $50,000. Of the cards of his that were from the original set, only 1 sells for more than it did 10 years ago, and frequently you can find Babe Ruth cards from 50 years ago for less than $30 - which is significantly lower than they were 10 years ago.
as to whether the person was paying too much or not does not really matter, what matters is that "too much" is a relative term. A $900 card might be worth $900 - but 2 years before it sold for $3000. From experience, and many years of card collecting, and 2 years currently running my own card-related store I can say, cards are NOT a good investment, whether it is a mint condition Babe Ruth or Rolly Fingers pack filler, they will ALWAYS decrease in value over time, and worse than that, the value of the dollar decreases so even if you sell the item for EXACTLY what you paid for it, you lost money. Items should appreciate on inflationary value as well.
There is only 1 real solid investment in this world, and that is real estate. everything else is destined to loose money.