In reply to llanberis36:
I've never laid a patio but I have fixed a garden path that was composed of slabs, I just put dabs of cement in each corner rather than fully covering the under-area with cement. It worked... sort of - it was none too perfectly flat and 1 out of about 12 or so slabs wobbled after all was said and done... and that's immediately after it was dry, no idea how many more started wobbling in the months and years afterwards.
Out of interest I just watched the Homebase "how to lay a patio" on Youtube and even for a moderate-sized patio, I think you'd be talking about 4 days of DIY work interspersed with 2 or 3 more days for letting cement dry but with the odd problem you could easily find that 4 days stretching to 6 or 7.
Might be worth pricing up the materials to find out where that 8k number comes from. A few ballpark estimates would be:
1k - slabs
1k - other materials
1k - 2 workmen for 2 days
1k - profit
1k - tool hire/capital depreciation/work vehicle fuel + depreciation
1k - misc costs like unexpected snags, extra time to arrange materials drop offs or pick ups, etc.
But these are without knowing the size of your patio or how pretty the slabs you want are, if your garden is actually a fair size, these costs might all be too low. On the other hand, if you are literally looking at a 5m x 5m patio then this estimate does seem very high.
How many estimates do you have? If you have at least 3 and they are all in that ballpark then either a) You have a serious shortage of builders in your area, b) That is genuinely the cost to do a quality job and you are just underestimating through lack of knowledge or c) You are an expert at rubbing people up the wrong way and nobody wants to work for you :P
How much does the quality of the result matter to you? It's very unlikely that you will achieve the same quality and durability of finish as a DIY effort that a professional would.