Interestingly, A Tree Grows in Brooklyn is a VERY pricey first edition - it actually really surprised me when I saw what excellent copies were going for - in the 6000 to 8000 range.
A Room With a View - currently no really nice copies available - the ones that are range from about 3500 down.
She - there is one copy available for 23,000 but that copy is in excellent condition and is signed by H. Rider Haggard to his mother - one of a kind. Otherwise nice copies can be had for under 2,000.
Maurice, although written at the beginning of the 20th Century wasn't published until 1970 - it's fairly easy to find in first edition and pretty inexpensive.
The oldest Shakespeare available on the ABE is a fourth folio edition from 1695. It's very reasonable - only $245,000.
If you want to have some fun go to abe.com, click on "advanced search" up on the top left, fill in author name and title, and then tick the box that says first edition (and, if applicable, "dust jacket"), then where it says "lowest price" change to "highest price" and click search.