Steve the PS3 does not support IR and there is no universal remote on the market that can output Bluetooth commands to the PS3 at this time. So no matter what, if you want to use a universal remote (Harmony, Universal Remote Control, Pronto,etc) you're going to need an IR to USB dongle in order to use that remote to control the PS3.
At some point the future there may be universal remotes that can also output bluetooth (I'm actually AMAZED at least Sony hasn't offered one yet) but at this time the only solutions are the Nyko Bluwave, Logic3 remote, and Mike's PS3IRX1 dongle.
In terms of cheapest solution, it would be to buy whatever universal remote you want (ie Logitech 550) and then adding whichever of the dongles is the cheapest at the moment. Not to thread crap but the Nyko has been available as low as $9.99 with free shipping ($14.99 on Amazon at the moment). Having said that, there have been issues with the Nyko in the past (all resolved at this point but no guarantee the same or worse problems won't come up with a future Sony firmware update) and there's basically no after sales support. Mike has worked to make sure all the previous issues didn't apply to his unit and has said he'd update firmware in the future if needed (albeit at a cost).