Hi
Unless things have changed in the last 3 years I would say that we found large electrical goods cheaper than in the UK. I think our washing machine was something in the region of £130, the spin speeds are not like ones you buy here, but then clothes dry so quick it doesn't really matter. We have a very large fridge which was also much cheaper than here (sorry forgotten how much).
Before we went on our furniture buying trip, we made a plan of the apartment, and worked out what furniture we needed, and what would fit where. Then we used a page per room in a notebook to write a list, and put rough prices that we didn't want to exceed by each item.
When we actually went, the agent took us around for the major items, but we arrived the previous day, and had a look around Marmaris and got prices for things, theres loads of shops in the road where Tansas is for furniture, electrical items etc. Thats when we found out that some things like fridges could be got quite cheaply, so we got the agent to take us to the shops we knew were good. Although obviously some of the shops they took us to of course we didn't know, but because we'd done a bit of groundwork we knew what prices were reasonable. I think for some items we did get them cheaper than other buyers who just went where they were taken.
We did find that some items were more expensive than we had budgetted for - in particular the furniture for the balcony - but we did buy cane stuff, but we made up the difference on other items that were cheaper than we budgetted for. I think we may have spent more than £5000, and it is only 2 bedrooms, but we could have chosen cheaper items in lots of cases.
It depends how much time you have, but for quickness we bought most of our bed linen in Ikea here, its very cheap and things are packed very small, so it saved us time on the 3 days we had to furnish the apartment.
It took a few trips till we had everything we wanted, but on our initial trip we just decided what were essentials and concentrated on them.
We had a great time spending all that money, it was really exciting getting everything together, I'm sure you'll enjoy it. I think the key is forward planning!