Depending on what you want, some have very reasonable packages. You just need to 'shop' around. The ones I recommend won't be cheap because they are very very very experienced photographers who are well-known in the industry & their schedules are always very packed!
My maternity photo can be found here: Maternity
Ben's basic package is $150 for 1hour. I think it's more than enough if you just want the photos & make your own photobook by othering online (it's cheaper this way).