Re: used CHEAP trailer or used rollers
Used trailers are pretty easy to find, even here where they seem to rust away fairly quickly. I just picked up a mint clean 2400lb GVW full roller Load Rite for $300. It needed nothing at all other than maybe a new winch cable. Good tires, good rollers, etc. I've gotten several this year for a song. There's an abundance of free boats out there as well with perfectly good trailers. Pick up a freebie, dump the boat and your set.
I got most of my trailers that way, I've actually gotten my best trailers that way. (I found a 2005 Load Rite 3500lb single axle full roller last fall for free under a junk boat, $35 fee at the dump to rid myself of the rotten mess they called a boat was all I had in it).
Going out and trying to buy a ready to use trailer however will bring price quotes well over $500 up to $1500 for a good used roller. (I sold one of my old roller trailers on CL last month for $1200, and that one was over 30 years old).
A set of roller bunks may also be an option for a trihull, I have one here on a trailer with two 60" roller bunks on each side, and a set of keel rollers down the center. It works well on a Starcraft trihull even at low tide if I tilt the trailer.