Gua-Gua fare from Cabarete to Sosua is 10 Pesos, Caro Publico for the same distance is 15 pesos. I believe I paid 25 pesos to Puerto Plata the last time I went.
If you are going to POP from Cabarete, it's best to take a guagua, because you don't need to change cars in Sosua. The caro publicos have routes from Rio San Juan to Sosua and from Sosua to POP, which means you have to change cars and pay again, if you are going further.
It is best to have the exact change ready, because you will be asked to pay more being gringo/a.
Going on a guagua can be fun and it can be a nightmare, depending on the driver. On occasion I have counted 27 people, another time I prayed all the way home and one time I got out way before Cabarete, because of the idiot driver.
Motoconchos are ok in town for short distances, but I would never take one for longer distances. Also, they charge much more.