A great entry auto is the Seiko 200m (SKX007K1) for under $185. Very tough. I bought one before I deployed and wore it every day for 3 years with no problems. This watch satisfies all my minimum requirements... Auto with at least a day of reserve power, must have a screw down crown and rate to at least 200 meters, and last... be common enough that most watchmakers have prior experience.
I second that. I have that watch and it is my go-to watch for when I am wearing more casual attire. Another great value that I can vouch for personally is the Orient Mako (though I have gotten good reports from all Orient Autos). For $100, I am not sure there any watches that come close as far as overall value.