I'm sure this question has been beaten to death already. I already own the classic fallouts on Steam, but was wondering if I should just get them from GOG. I like my games to be on steam but it really isn't a deal breaker. Would it be worth it?

Also, I thought I remember seeing the classic fallouts on sale here at GOG for $10, right now all 3 go for $15.

Fallout 1 was free at one point, 2 and Tactics have been on sale at least twice in the last year (50% off iirc). Unfortunately you missed the boat on those. If you prefer Steam then you may as well leave it at that and not buy them again here.

Worth how? You have them already and like steam.
Gog versions have pretty good extras, fallout bible, soundtracks, wallpapers, avatars, stuff.
But it's hard to quantify what's that worth to you.

I had 1 and 2 already as boxed, but got them anyway when they were on a sale here.

What happened Fallout 1,2 and 3 pricing? They used to be 5.99$ each and now they are 9.99$

Same as on steam, but that doesn't mean that it isn't still a bargain. 2 is the best rpg I have ever played.