What's the value of my 64 VW beetle convertible ?

If it is a true '64, then it is not a Super beetle. I had a "flat" window 71 super and know a bit about them. 71 and 72 are the only years that the super had the flat front window, all others have a strong curve. If the window is curved, has spring mounted struts and a flat laying spare tire well in front, it is a Super Beetle. Value, a 64 is worth more than a 74, given equal condition, and quality counts. Just to properly replace the top could be 2000 or more in US dollars. Perhaps 1000 for a do it yourself kit.

Take whatever the guy is asking.

1964?Try 74 That MIGHT be a Super if it has the curved front windshield, as VW did make regular beetles too(flat windshield)at the same time. It is just a Beetle Ragtop, it is as valuable as one wants to pay for it AND NO MORE. Look closely at the tail-light lens. There is a raised number in the lens plastic. If it is 73 then the car is a 74.  If you had supplied the vin code should start 113(superBeetle) If code starts 111(regular beetle) which is on the dashboard and you can read it from outside and look through the glass that would tell us more. SB is also known for the curved windshield and Macpherson strut  front suspension.  Stock beetles had torsion bar suspension.  The front tire is laid flat like a table top inside the hood so it bulges a little.  On stock units the spare tire sits nearly upright in the front.  VW could have built both versions, or somebody started customizing his bug to be different. so it is NOT factory.  If that has happened, then you have a bastardized bug.  Not worth anything to collectors.  Basically a piece of tin. Maybe you get $75 if you tow it to a junk yard.  They in turn will sell parts from it for total of $10K but that is their business, not yours.

. If it is a 74 then again it is worth what somebody will spend.

My neighbor got a 71SB hardtop for...wait for it...$300.  It is all there, but the engine does not turn over(meaning there is a problem)  Auto salvage, he could get $300 so no loss. Some rust where the battery goes and to score the driver's fender is not costly or difficult to acquire.  As it is, Auto salvage yards will part it out and probably make $2000 in parts(maybe higher)

The Super Beetle did not come out until 1971, so your car is likely a 1974.

Parts being "there" is meaningless without much more info, and pictures. Do all parts work? Does the engine start, run, drive, charge the battery, can it even roll? Also, do all the lights work, radio work, condition of the rockers, is there rust, where, no roof means a lot of interior damage is likely, was it stored in a building or outside, are the seats in good order or are they as rotted as the roof.

If the car is mostly rust free and is just basically a mouse nest, you may get up to a thousand bucks, if the engine turns over and it can move under its own power. There is a lot to do to make it serviceable again.

I do not like convertibles as they are usually money pits, even with low rot.

If your neighbour is the only one interested it's worth what they are offering.

Look at prevailing prices on classic car websites.

All the expensive things need replacing ,What are they offering?

many cars will sit in sheds never to be rebuilt as the owners think they are worth a fortune. Get many an old car for free do it up and sell it you still lose money.