There are other approaches which are cheaper. However, the easiest are probably limited to 4 inputs and one output.
You can look for consumer-grade A/V switches. www.smarthome.com used to carry one from Emerson. I don't see it on their site, now. It uses an IR remote control to select the input - so you should be able to control it with IR from HomeSeer. Radio Shack also used to carry a switch that responded to IR. It did not come with a remote but was designed to learn from any remote you want to use. This should also work from HS.
I'm sure there are other similar switches around that are controlled by IR. There are also switches that will automatically switch to whichever input is active. These are harder to work with if you are going to have multple inputs on at the same time.
For a nice clean solution like the ASEL or AVS units from www.controlanything.com, you will probably have to pay more from other places rather than less.
I would like to get an
avs-8x8 from www.hacs.com. They run $200 but allow 8 outputs to connect to any of 8 inputs.
You can also build your own. I think zoomkat has outlined a relay/transistor/parallel port solution on the HomeSeer boards.