If you check the donation address [1] as its linked under donate you will see that the last donation for 50 BTC was in 2011[2].
Code:
2011-08-29 18:27:47
oldest price I could find on bitcoincharts [3] is from 2011-09-13 ~5 USD per BTC. The donations come from a time when BTC wasnt worth as much. It was discussed often if the amount to donate for VIP should be lowered, but theymos and others in charge think it would not be fair to those that donated 50 BTC in the past. I also think its a good idea that VIP essentials says: I have been here a long time and I believed in it. If the amount to donated would be lowered to e.g. 0.4 BTC (~ equivalent in USD to 50 BTC 2011) we'd see way to many VIPs.