in the uk they can range from £150 if badly presented up to £300 if shill bidding/very well formed listing/minty condition is involved.
They are one of the cheaper synths as they sound really dated (Imo) almost like no other synth does. I bought mine for £60 with a case and synth1 cards and a ram card!!! And parted it out for way more than they are worth sold as a unit but that's not for everyone.
If you are putting it on ebay then just leave it to auction, they are far from rare (the most popular synth of all time!) and come up daily. Anything around £150 is fair game imo and depends on condition. Maybe start the auction at £150 if you don't mind possibly selling it for that. Otherwise, clean it up take some great photos do a detailed listing and put it on buy it now at £275 and it should shift - if you wanna hold out for £325 I would say that's the upper limit (though have seen them go higher on mad days) but you may find it takes longer to get a buyer.
£200 is a more than fair price all round if in good condition. I wouldn't buy one for more than £100 though but that's just me.
Moog SUB 37 | Juno 106 | Polysix | JD-800 | SY77 | DX7 II-D | Performer
HAD:SH101/JD-990/V-SYNTH/JUNO 1,2,6,60/MKS70,50/JX3P,8P/D50,70/JV1080/AX80/SY77,85/DX7,IID,S,100 /TG77,500/TX802,81Z/AN1x/ MS2k/DW8000/PROPHECY/W-STATION/M1/CZ1