You can download a WinRunner demo from Mercury's website. It's a very basic demo of their record and play capability. You need to contact Mercury for pricing information. Having just gone through this exercise, it is not as simple as it sounds. Their protocol is to schedule a visit which allows them to get a handle on what you are looking to do and see how much $$$ you have to spend. Contractually, you are not allowed to discuss price with any other parties.
I can add something to this. Their "Protocol" in the UK must be slightly different to the of the US because you do have the option of choosing an online demo, straight user eval or site visit. Most vendors will offer a site visit especially if you "Wave a carrott" (lots of money) infront of them.
"if it works, leave it well alone....if it does not work......ditch it!"
if it works, leave it well alone....if it does not work......ship it!