I bought 2 x 64MB sticks of RAM for my Sun ULTRA 5 off eBay the other day for the huge sum of US$6.00. Postage made it AUS$18 which I thought was reasonable. Here's what's changed:

These graphs were taken over a two day time period, and the change was significant I thought. Now the Sun isn't paging out to disk anywhere near what it was previously (which was all the time) so it's running much faster and appears more responsive.