$3500 is a good price
Do some research 1st and have your builder make any custom modifications you may want.These mods are what I use to ramp launch,very heavy duty tongue roller to carry full weight on rough surface,tongue ladder all the way to deck level,padded adjustable guides that extend above water when the trailer is submerged, underwater keel guide to make sure boat lowers into exact place 1st time everytime, bow chock and winch, stronger axles and tires than you think you need but only two axles (don't get mobile home stuff, it's too tuff to find parts etc.)be sure to have builder mount a spare tire,have builder make supports removeable so you can clean entire hull when on the hard, consider a mast raising system, your builder can throw it together for next to nothingOf course if you always use a yard and sling you wont need some of this stuff, but it's worth thinking aboutHappy Trails