Rode to Timbuktu (rough but has to be done), put bike on pinasse back to Mopti, approx euro50 from memory incl food. Recommend a private one over public, comfort a big reason, but also safety. When I saw how low in the water some of them were I knew I had made the right choice! Price seems to depend hugely on demand - they have to get the boat back up to Mopti, passengers or no passengers. Three days of enforced idleness - read, shoot the breeze with fellow passengers, sun bathe, pull up in evening to camp on a beach, slip off briefly in Niafounke to pay respects at Ali Farka Toure's family house, sub Saharan desert scenery, mud mosque Niger villages sliding by... Very fond memories of that three day trip.