What are these R. Crumb comics worth?

[Meroigo]

My dad has alot of comics from R. Crumb and there is two he says is worth the most. It's one called "Mr. Natural" and I can't find anywhere in it what volume and number it is. The other one is the first volume and number of "Home Grown", printing number 10.

Both are stored in plastic cases and they are well-read over the 30-35 years they have existed, but my dad has been very careful with them.
You can say that they are not in a perfect condition, not the condition before perfect, but the condition before the last mentioned (OK that was pretty weird expressed... but that's how my dad described the condition).

I scanned in the front page and the second page of both comics, so that you can read the copyright and printing text in the bottom of the second page for both ones and maybe find more informations on the pictures.

Home Grown front page: http://jts.mine.nu/Temporary/comics/homegrown1.jpg
Home Grown second page (MATURE CONTENT and with a funny copyright text in the bottom): http://jts.mine.nu/Temporary/comics/homegrown2.jpg

Mr. Natural front page: http://jts.mine.nu/Temporary/comics/natural1.jpg
Mr. Natural second page: http://jts.mine.nu/Temporary/comics/natural2.jpg

Now to the question... Are they worth anything? And does someone know what they can be worth?

[Corsair]

www.comicspriceguide.com lists the 10th print Home Grown Funnies as $5.00 in near mint.

According to this site (http://www.ugcomix.info/guide/M.html) the Mr Natural #1 with a 75 cent cover price is a 7th printing. I can't find a value for it, but I see a couple of recent eBay auctions with earlier printings that went for around $15.00.