Because of the number of styles available, solar lights vary widely in price. Simple solar post lights can be as low as $5 each, but it may be better value to spend a little more on a reputable brand. Ask for advice from your hardware store. You can find lots of good deals online as well!
Good quality solar flood lights might be $60-$80 for a small set of 3 or so. However you don’t need as many of these, as they are intended mostly to illuminate features in your garden. One or two sets of flood lights hould be enough to pick out the key parts of your garden at night.
Good solar tube lights might cost around the same as a set of flood lights. These are designed as a continuous string or tube of flexible lighting, and can be sued to great effect to decorate the edge of a water feature or wind up a tree.
Ornate lights like statues, imitation stone, etc will be the most variable but expect to pay at least $50.