Copper
Figure the average tour is 75-90 pp, Mayfield Falls, YS , Black River: Snorkeling and Sav market can be done for much less but the main attractions are as stated. I spend 80ish a day on too much alcohol , too little food, and a taxi ride or two a day traveling solo.
Keep in mind when people start preachin about sand gravity will keep you from doing all the tours you think before you go, I think those that say that do not travel solo because who the heck wants to sit and talk to themselves. If traveling solo making drinks and meals in your room is pretty impractical as well as sand gravity kicking in; because again I mention who wants to eat and drink alone in your room or spend all day alone on the sand. You can stay at Home and do that. Get out and see it all, see everything you can afford because it isn't things you have at home, you are there make the most of it.
I would take $1500 if I were in your shoes, 1200 at the least. Without any tours I would take 1000 for 12 days.