It's totally legitimate for a professional to charge you for a design, at least in some situations. If the contractor has a book of ready-made designs and just pulled one out to show you, then you're right that s/he shouldn't charge you. But if someone does a design that conforms to your room's dimensions, with the features that you want, then that person has invested time in creating a work product. Some contractors and architects think that's just the cost of doing business, but many others consider that their time is worth something, and they charge for it. You just need to let contractors know that you're not looking for that kind of custom work, and not willing to pay for it.
The more luxurious the materials for a bathroom remodeling project, the higher your budget will be. Using marble for your counters, custom cabinetry or handpainted ceramic tiles for your new shower walls in the master bathroom will look terrific. But it will also raise your material costs considerably more than installing a laminate countertop and low-end or mid-range tiles.
There are a wide range of costs associated with remodeling a bathroom, including size, the type of materials, its current condition, and the location. Homeonwers spend on average between $15,000 and $25,000 in their bathroom renovation. For example, the average cost of a 100 square foot master bathroom with tile walls and flooring, new fixtures, double vanity, and walk in shower with separate tub is around $20,000.