The price as it stands now is simple. Take them to a couple places who buy bulk silver and get a price. If you want more than that- you need to do the following:
Go online and printout a list of the key dates for washington quarters.
sort all 1500 of them, by decade first, all the 30s, in one jar, 40s in one jar, 50s in another jar, etc, then sort by year. This way you can determine if you have any of the key dates, 1934 D and S, `1934 DDO, 1937/42D/43/50 errors I dont remember what all of them are so look online.
Assuming you have some key dates, get them looked at by a knowledgable person to determine the grade- or buy the ana grading book- OR- you can use photograde on another website. Then you can sell those coins on ebay and sell the remainder by the roll for melt value.