Origin

The post-adjective "much?" construction has been used for ironic emphasis at least since 1978. As it was documented in this SNL sketch:

October 7, 1978, episode (Season 4, Episode 1), with The Rolling Stones as host, the teen nerds Lisa Loopner (Gilda Radner; William Safire (1992) spelled it “Lupner” in On Language; Not! New York Times Magazine. March 8, 1992, 20.) and Todd (Bill Murray) are hanging out in Lisa’s kitchen:

TODD: I really need your help with my history homework.

LISA: Well, Todd, you know if you sincerely need my help, you can count on it.

TODD: Oh, good. Because I’m studying all about [grabs at Lisa's shirt neck and tries to peek down her shirt] underdeveloped nations!

LISA (shouting and smiling): Cut it out, Todd! Cut it out! [lightly swats him away] Stop it!

TODD (points at Lisa’s chest and mock laughs to a pretend audience): Underdeveloped much?

Spread

The term gained notoriety especially in the 80s and 90s as the ironic generation "X" developed. Frequently used in series like "Buffy the Vampire Slayer".

The OED was quite recently updated to include this use of "much".

colloq. (orig. U.S., freq. ironic). With a preceding adjective, infinitive verb, or noun phrase, forming an elliptical comment or question.
The use was popularized by the film Buffy, the Vampire Slayer and the television series derived from it.
1988 D. Waters Heathers (film script) 15 God Veronica, drool much? His name's Jason Dean.
1988 D. Waters Heathers (film script) 86 Heather Duke. It was J.D.'s idea! He made out the signature sheet and everything. Now will you sign it. Veronica. (queasy) No. Heather Duke. Jealous much?
1992 J. Whedon Buffy the Vampire Slayer (film script) 8 A stranger, walking the other way, bumps into Buffy, doesn't stop.‥ Buffy. Excuse much! Not rude or anything.
1992 J. Whedon Buffy the Vampire Slayer (film script) 25 Pike and Benny have entered the diner, quite drunk.‥ Kimberly (to the other girls) Smell of booze much.
1998 M. Burgess & R. Green Isabella in Sopranos (television shooting script) 1st Ser. 1 42 Anthony Jr. Probably I can't go to that dance now either. Meadow. God, self-involved much?
2001 Cosmopolitan Dec. 178 You've seen them: the kinds of couples who finish each other's sentences.‥ Jealous much? Damn right.

External References

Buffy (and SNL) ‘much’ much?: Slang research with Hulu.com, Part 2
UPenn X much