I paid $1,800 for a fair condition 1970 DS I with very worn sails and a poor condition trailer. This was probably a somewhat high price. Location matters. The boat was on the dock and ready to launch when I bought it. There was no need to transport it any place. Everything was in working order and still is.
My DS1 #249 with a nice trailer and two sets of sails, unused spinnaker and several spare tires for the trailer cost me $1500. I hauled it about 300 miles from Houston to Ft. Worth. It sailed perfectly well right off the trailer, requiring only cosmetic improvements (Dear Wife wanted the boat primarily for the opportunity to refinish REAL mahogany).
My DSI (circa 1967) was purchased from a friend of my father's who has too many sailboats, for $400. It included somewhat rusty trailer with good tires, worn sails, all mahogany coamings and floorboards, all in great working order. I realize that this was a better than average price than what I have seen out there.
Depends....is the boat a Day Sailer I, or is it a Day Sailer II? I ask because a Day Sailer I is in higher demand (for racing) and so may be "worth" more.
Check the link from the DAY SAILER HOMEPAGE for "Day Sailer Value" It takes you to the NADA website which lists prices/values for most boats from about 1966 to present.