I bought a new heavy duty 5x10 uility trailer several years back for $500 cash. I later picked up some 5" channel (4" will work) from a scrap yard for $35. I had a buddy with a weld shop modify the channel for the bikes for a little barter work. It will haul 3 bikes with room to spare.
The whole thing with tags cost less than $600. The good thing is that it has either 14" or 15" tires (easy to find used tires everywhere) and you can drag it 80 mph and go any where unlike the trailer with small tires. I go off road, over rocks, up mountains, through rivers, you name it.
After 15 + years of dragging it behind me, I greased the wheel bearings, replaced the bottom wood with treated lumber (paint the wood top and bottom good when you get it - my error!!), and the frame needs a paint job now. Ready for another 15 years.