[Pricing] Basic Mewtwo 51/108 Card Value Estimate

[pswinz]

Hi there, my son is 8 and thinks he's found a valuable card. It's a Mewtwo basic 51/108. I've tried looking it up on eBay and the prices are extremely varied. Is there anyone who can assist with determining the approximate value? It appears to be in excellent condition w/ no damage. Any help would be much appreciated!

 

[icycatelf]

Any other version of this card (Base Set, Japanese holo, reverse...) would probably be worth more, but this version only looks to be going for around $2-3 at the moment.

 

[pswinz]

Thanks so much for the response.