Buying lower means a lower exit is required to get the same multiple. So buying lower is always better for a VC. Worst case they make less money on the same multiple, better case they make a much higher multiple. It's all about the rate of return, not the actual amount (assuming the amounts are still worth the effort of investing, obviously there are some lower bounds here).
If the buying price of Y goes on a 75% sale, while the selling price of 10Y also goes on a 75% sale[1], the VC makes 75% less money.
[1] Things usually don't go that way. Smaller prices tend to fall less than big prices, and the VC will almost certainly get into the negative.