the cost of lens cleaning is depends one where is a zoom lens or prime lens, prime lens are cheaper, but will not cost a few hundreds for cleaning a zoom lens. anyway, a simple lens clearing service charge is able to buy a small size dry cabinet already.
remember, prevention is always better than cure, don't take any risk for letting fungus grow on your lens.
btw, fungus spore is airborne and it is present every where, so your lens might already has fungus spore land on it, what fungus needs is just the right condition to grow. So don't push your luck, raining season is coming.