Do you know the per hour burden rate is for each employee that item has to pass through before it lands on a service tech's bench? I'll give you a clue, it's way more than the simple hourly rate and benefits for each employee. For our company that could be around $100 or more per hour. Things like supplies, office space, furniture etc. gets lumped in that rate, at least for us.
For people you have the receiving clerk's time. Next is the person in aftermarket that that has to generate the RMA paperwork, and track the progress of the repair order and then arrange shipment back to the customer. The shipping clerk's time. Shipping and insurance costs. Then the bench tech's time, from my experience sending in radios for minor work that gets billed at $125 per hour etc. The costs add up. For some items it's just not worth sending the stuff back.
I've gotten a few digital mode bum radios on eBay I've paid $150 to $200 for. The seller refunded the cost just told me to keep the defective radio. I was told it wasn't worth the cost to them for the return. I did send those in to a repair depot. In the end I ended up spending about the same amount of money between the repair and shipping costs. Basically broke even.