Is "Thanks so much" wrong?

I have seen many many people say "Thanks so much". I believe what they really mean is "Thank you so much".

Searching "Thanks so much" in this website gives 177 results. But the questions deal with "Thank you very much" or "Thank you so much". See e.g.: “Thank you very much” vs. “Thank you so much”

I personally think it's wrong usage. But I've seen many people use it that way. Is the usage really wrong?

-- EDIT --

@Kevin Workman, I think it's wrong because

1) "thanks" is a plural noun in this context and can't be a verb since it doesn't make sense to say "I thanks ..."

2) I remember been taught that "much" shouldn't be used with countable nouns in plural. e.g.

From http://www.ego4u.com/en/cram-up/vocabulary/much-many:

many friends
much money
many thanks

But what about "Thanks very much"? Does a different rule apply here?

-- EDIT2 --

I originally thought "Thanks so much" were wrong because the many people I saw saying it were non-native speakers. From the feedback here at E L&U, I got suspicious and asked a couple of native speakers. To my surprise, they both said it's OK. One said it's informal and "many thanks" is too formal, and the other said yeah there is that grammatical issue but it's OK (after I asked specifically about it).

My question is now theoretical and reduces to how to restore "Thanks so much" or "Thanks very much" to a complete grammatical form without omission. For example, the seemingly incorrect "two milks" can be restored to "two measures of milk". What about "Thanks very much"?

@Sven Yargs suggested an interesting theory that "Thanks" is interchangeable here with "Thank you". I am still a bit suspicious though as many things could go wrong with substitutions in grammar.

-- EDIT3 --

The latest development I see in emails is "Thanks much!". This is about one step away from "much thanks"...

Phrases like "Thank you", "Thanks", "You're welcome", "No problem", etc, along with other phrases like greetings/farewells ("Hello", "Good-bye"), are just set words and phrases. They don't form complete sentences with subjects, verbs, etc.

If many native speakers are showing their thanks by saying "Thanks so much" then it must be acceptable. It may be considered informal, but it's hard to see how it can be "wrong", or more wrong than just "thanks".

My sense is that "thanks" originated not as an inexplicably number-confused version of "thank you," but as a short form of the related (but different) expression "my thanks."

As the OP evidently recognizes, "thank you" may be taken as a shortened form of "I thank you"; and the longer form "thank you very much" works seamlessly from that base. But "thanks" surely does not trace its origin to "I thanks you"; it is far more likely to have originated with "my thanks," which in turn may have been extracted from a longer-form idea such as "please accept my thanks for xxxx" or "I offer my thanks to you for xxxx."

Undeniably, "my thanks to you very [or so] much" is an awkward expression, but it's not incoherent if you read "very [or so] much" as meaning "in or to a very great degree." Still, I doubt that "thanks very much" began as "my thanks to you very much." Instead, I suspect, English speakers (in the United States, anyway) became accustomed to treating the truncated forms "thank you" and "thanks" as completely interchangeable, which led them to begin applying the "very much" (or "so much") extension that originated with "thank you" to "thanks," as well.