I agree. If you can get $10 large for Invincible or any modern book for that matter, I would cash out in a second and look to buy a major SA key like FF1, AF1, or something of the sort. Even a 0.5 of those books is still a better buy than a modern.
I'm not saying Invincible, or any modern is worthless, therefore Sell, Sell, Sell.
IMO (again) The Walking Dead (tv show) was a cultural phenomenon, on basic cable, lasted multiple seasons, a spin-off, and the high for a 9.8 was $2500 (note: "was" the key word, before all of this nuttiness, in the TWD heyday. I just looked it up and I guess it's around $3500 now).
Invincible is a cartoon (it may be good and "adult" but many people will be turned off b/c it's animated), on a streaming service, has a single season under its belt, and a 9.8 can fetch multiples of TWD? No brainer. (And I'll say it: JK Simmons voice acting was downright rough at times.)
Though some moderns are looked down upon, they are more of the overall market than SA keys; new issues come out every Wednesday and moderns are more heavily bought/sold than any SA key.