I was looking at the Radiosouth site and I noticed the pricing it quite significant. I can see for higher end radios and servo, because I guess this price is only a fraction of the cost of getting new stuff. Is there a point in sending in like a 4-channel non-computer radio, with 3 standard servos? Between the shipping costs to and from, plus the cost of new parts, plus the labor charge, I think it might be more expensive than just buying new.

You might be right. But, maybe not for a higher end computer radio. Perhaps that's what you should do if you find the pricing excessive. Or, send it back to the manufacturer for repairs and calibration.

Also take possible warranty into consideration when deciding where to have service done.

As mentioned, a 4-channel system may not be worth the hassle and expense to service. I recently sent in my Futaba 6XAs and was only charged $55 for inspection, repair, and retuning. If you do decide to send the radio in for service, be aware of the fact that during flying season (summer), most any service center will be pretty booked with repairs. Mine took nearly a month, but in the end I feel the expense was justified (for a 6 channel computer transmitter). What exactly is the problem you are experiencing with your radio system? I was experiencing random glitching and after testing with different receivers/crystals I concluded that the transmitter was the cause of the issue. Radio South found the issue and fixed it, and I saved myself some money by not having to send them my entire flightpack for inspection. HTH