That depends on a number of factors. Is it complete meaning does it have every single part it orginially came with? Is the color still bright like brand new? Is it in orginial packaging? Are there any flaws in the figure itself? Chips, nicks, or broken and repaired limbs?
The short (and a bot flip) answer is that it is worth whatever someone is willing to pay for it. The best answer is to do some research on your own. Sadly, collectibles are sometimes a difficult area. I suggest checking with any local collecting/comic businesses that might be in your area. Talk to them about what condition the figure is in. Also check places like eBay to see if anyone is offering the figure for sale and what condition and price they have listed for it. Keep a watch on it and see if it sells.
Unfortuanely, there is no flat "it's worth (insert amount)" answer without some research on your own. Sorry.
Maverick - 1957 was released on: USA: 22 September 1957
Maverick - 1957 The Maverick Line 4-10 was released on: USA: 20 November 1960
Maverick - 1957 Trooper Maverick 3-12 was released on: USA: 29 November 1959
Maverick - 1957 Alias Bart Maverick - 2.3 was released on: USA: 5 October 1958
Maverick - 1957 Maverick and Juliet 3-18 was released on: USA: 17 January 1960
Maverick - 1957 is rated/received certificates of: Argentina:Atp Australia:PG
Maverick - 1957 Alias Bart Maverick 2-3 was released on: USA: 5 October 1958
Maverick - 1957 The Day They Hanged Bret Maverick 2-1 was released on: USA: 21 September 1958
Maverick - 1957 Hostage 1-8 was released on: USA: 10 November 1957
Maverick - 1957 Stampede 1-9 was released on: USA: 17 November 1957
Maverick - 1957 The Jeweled Gun - 1.10 was released on: USA: 24 November 1957
Maverick - 1957 The Jeweled Gun 1-10 was released on: USA: 24 November 1957