AG dolls are indeed expensive and do not go on sale, ever. AG does not do coupons either. Sorry, no such thing as "wholesale" for these -- AG controls the pricing tightly. But I must say: The dolls are very high quality and last longer than the knockoffs, have better hair for styling, etc.
Dolls come with an outfit as well as, usually, a sort of starter kit with a few little accessories (handkerchief, necklace, lucky coin -- whatever's part of that character's story).
Buy clothes from anywhere. There are lovely handmade clothes online that are a bit less than the AG store ones. Yes, Michaels has clothes that "fit" them but I found that the fit is always a bit too tight.
For accessories -- let your daughter MAKE them. My kid has made a lot of things including a bathtub (shoebox covered in foil, lined in blue paper, fillled with cotton ball "bubbles") and a vanity (box covered in different papers, "mirror" of tinfoil, perfume bottles of stacked and glued beads, etc.) Encourage her to be more creative than just playing with only store-bought accessories. Then get her an occasional outfit or small accessory, just one, for the next birthday or whatever.
Most of all, get her the books that go with Isabella! The books are usually well-written. My daughter loved all the historical character books. Those are in libraries and I recommend them all-- it's fun to read them with your child, in order to tell a particular character's story. The "girl of the year" dolls like Isabella seem to have only three books each whereas the older historical dolls had six -- which was great.