When I was looking for a Defender and was the purchase viable for me I looked in depth at the cost of spare parts.
I was totally gobsmacked as how inexpensive everyday parts were (service parts and wear parts) you know the parts you would typically need to keep a Defender on the road. Ok I did not price them at a main dealer but from adverts in Land Rover mags and looking at the likes of John Craddock, Paddocks, MM4X4 and others on the internet.
Defender purchased and as you can imagine it was not long that I needed to replace something, Door seals because I was getting wet, off to one of the suppliers mentioned and two new door seals from Britpart in my sticky hands. Returned home to fit them could I make them fit and seal properly not on your life could I. Tried to return them but they were not having them saying they had sold many and never any returns just take care and they will be as good as the genuine ones or we could fit them for you (at a cost). Stuff this for a game of tin soldiers went to main dealer two new genuine seals fitted in no time and the doors shut easily and seal. Cost difference Britpart £12.18 for the two and LR £114.02 for the two.
In the coming months I purchased a number of things mainly Britpart I was not enamoured by the quality but the price was good.
In a very short time these replacement parts started to fail in what I believed was not a useful service life, Getting disillusioned with after market parts quality at the point I purchased a transfer box HI/LOW switch which was a blue box Britpart part and when I opened the box to fit it, it has fallen apart in its packaging. In a fit of temper I chucked it down the garden and said that's it no more after market parts only genuine.
I believe I have had to replace all the none genuine parts I fitted because they have failed except for door mirrors (but I did have to modify them to stop them vibrating).
You get what you pay for but it has made ownership a lot more expensive than I had budgeted for.