You'll spend about $7,000 and up for a kit for the 1500, depends on the brand and options. Remember, you only get what you pay for. I had an '89 with a popular, cheap brand kit and it actually fell apart while I was riding it! This website lists about 12 different manufacturers of kits, most include prices http://www.redmondtrikes.com/index.html /
When the Voyager first came out I saw a lot of them at rallies. I saw very few last year and less this year. I have read a lot on boards about the problems they are having with them that some are solving by welding in extra pieces for support. Personally, I'd go with a regular trike if you want to do any long distant riding on the interstates or at high speeds.