A couple of changes have been made to the Grand Exchange, so that item prices can more accurately reflect player demand.
Maximum price cap change
Many non-stacking items are considered to be worth more than they cost in a shop. This is because it can take a long time to ferry these items from the shop to your bank. The Grand Exchange will now account for this, and therefore the maximum price cap for these items has been raised.
Minimum price cap change
The Grand Exchange previously capped the minimum price of items at the amount you could get from a shop, but failed to account for the fact that when selling in bulk the shops would give much less. This has now been fixed, the result of which is that for certain items, the minimum price cap on the Grand Exchange has been lowered.