Nice ray.
May i suggest removing some of the sand, keeping a deep sand bed with rays is dangerous business, deep sand can encourage anerobic conditions which will kill your ray. Almost all experienced ray keepers recomend a sand depth of 1/2 a inch or a bare tank bottom tank.
The price of rays really depends on their size, they grow quite slowly so the difference in price between a 4" ray and a 6" ray can be quite significant, i paid £90 for my 6" motoro so around £50 or £60 is about right for a 4 inch specimin.