use 1 1/2" pvc pipe and I have shipped thousands over the last 10+ years and only ONE was ruined and that was by Airborne Express when they drove over it with a forklift. My standard shipping costs in the Great 48 is $20.00 and $5.00 for the pipe and caps. Yes, that is a little low on the price for the pipe and caps, but that's because they have gone up over the years. USPS will ship your mast for about $18.50 so it evens out. That is of course a naked mast, no spreaders, no attachements that would prevent it from sliding in the tube. You will have to suppress the laugh when the PO worker attempts to measure the height and width of a circle.. and the idea of π d never enters the process.
*Note that in this case, and many others, it is actually cheaper to use USPS PRIORITY than it is 3rd Class. They recent change in rates 30 days ago I believe still bears this out. UPS can come up $1 - $2 cheaper.... but USPS will pick up from the curb, and I don't have to take it anywhere or pay for a pickup. FedEx is always the most expensive, I only use them when the customer requests it
