If you're selling the entire set retail, a fair price would be around $250.00. If you go to a dealer, you'll probably be offered around $175.00. Now that's the short answer. Some years are more valuable than others. The 1999 set is worth around $35.00 retail where the 2000 set would be only $10.00. the 2001 jumps back to $35.00, then from 2002 through 2007 only around $15.00, then back up to around $35.00 for the 2008 & 2009. There wasn't a state quarter set for 2010.
Unless the quarter is in mint-state or a proof, the value would be the melt value of the silver in the coin which is $3.80ish as of this time of writing, but changes depending on the spot price of silver.
There aren't 112 proof state quarters. There are only 50 proof state quarters, (along with 6 in the DC/US territories). Unless you are meaning you had both the clad (copper-nickel, common) proofs and the silver proof sets. But just about every clad US proof state quarter is worth about $1 or so, silver proof quarters go for about $7-8 or about fifty cents or a dollar above melt value individually.
A 1999 US Mint 50 State Quarters Proof Set is worth about five US dollars. However, a 1999-2008 US Mint 50 State Quarters Proof Set is worth about 100 US dollars.
A 1957 quarter is worth about $3.75 in top circulated condition. Uncirculated quarters are worth up to $14 and proof specimens are $8.
As of 07/2010 the average price for a 5-coin silver SQ set is about $24. Some years are a dollar or two higher but there are no significant differences.
25 cents
It depends on what state it was issued for, post new question
....25 cents just like any other post-1965 non-proof quarter. State quarters are not rare or valuable unless they are proof or have some error.
If you mean a 2005s proof California state quarter retail is $1.10
Unless the quarter is in mint-state or a proof, the value would be the melt value of the silver in the coin which is $3.80ish as of this time of writing, but changes depending on the spot price of silver.
1974 S (Proof) Quarter is worth $1.50.
Unless it's Proof, it's just a quarter.
A 1999-S Delaware Silver Proof Quarter, certified as a PR-70 Deep Cameo example has a listed retail value of $3,000.00.
Averge retail value is $2.00 for this coin.
If you found it in change, it's 25 cents. The retail value of a single proof is about a dollar.
A 1988 Proof Quarter is only work the face value, for the most part. To some collectors, they might be willing to pay as much as $18, but this is rare.
The Georgia State Quarter has a face value of 25 cents.