As already mentioned, exotic vet costs will vary. Here in the States they can charge from around $25 to $60 for the office visit plus the cost of medication. One of my does had mites in the past and it was $37 for the office visit plus $15 for the Ivermectin. Most vets will treat all of your rodents for a parasite problem without making you bring them all in if you have brought one in that has an issue as chances are good they all have it. You will have to pay for the medicine, of course, but you avoid additional office visit costs. What kind of products did you try from the pet store? Many of the ones for rodents just do not work. There are some OTC (over-the-counter) medicines that do work on rodents to get rid of parasites. For instance, horse wormer paste, which is Ivermectin, treats mites and lice. Spot-On treats mites. Revolution treats fleas, mites and lice. Advantage can be used for lice and fleas. I shall give you further information on the above OTCs from a reputable rat site