https://asicminermarket.com/product/l3-litecoin-miner-250mhs-400watt/Your titan is 400? MH/s @ 1300w @ the wall.
This is 250 MH/s, 150 MH/s less.
With the 250 MH/s L3, this is your profit at 10c /kWh: 119.15 USD / month
https://www.litecoinpool.org/calc?hashrate=250&speedunit=MH%2Fs&difficulty=102398.53515485&price=3.8996¤cy=USD&power=400&energycost=0.10With 400 MH/s, 1300w @ the wall:143.12 USD / Month profit (At current diff).
At your cost, around £2500, it would take 25 months to ROI provided diff remained the same, which it isn't as new hardware is coming on the network pushing it up. So an already 3 year old miner would need more than another two years to ROI if diff remained the same.
The monthly profit of the bitmain is lower, but the price is also £800 GBP lower roughly, and as it is new hardware with a warranty your chance of hitting ROI are better.
You are asking 3.8 BTC. for 4 BTC i can get TWO bitmain units, which would at 500 MH/s at 800w at the wall at 10c / kWh would give me: 238.29 USD a month profit, just under $100 more a month than your titan, new with a warranty from Bitmain.
https://www.litecoinpool.org/calc?hashrate=500&speedunit=MH%2Fs&difficulty=102398.53515485&price=3.8996¤cy=USD&power=800&energycost=0.10Titans used to go for insane prices due to the profit and I made boatloads of profit from my titans and sold them all off just before Bitmain announced it, but even then i got £2000 for one, £1750 for another which was a fair price. Now though, you will not sell one for 1.5 BTC, let alone 4 due to the diff increases.
My 1 - 1.5 BTC offer for one of these will stand if you wish to take it, i understand if you don't if you have already ROIed if i were you keep it plugged in and mining as you may make more in the long run.
So we have a comparision:
1. Your titan - 3.8 BTC + Shipping + Customs duty to UK would total 4 BTC probably for me. 4 BTC ($4000, $143 a month profit at 10c kWh so a 30 month ROI if diff remains the same (it wont))
https://www.litecoinpool.org/calc?hashrate=400&speedunit=MH%2Fs&difficulty=102398.53515485&price=3.8996¤cy=USD&power=1300&energycost=0.102. 1 Bitmain L3 - 1.94 BTC + Shipping + Customs duty to UK, totals 2.1 BTC for me. ($2100, 119 USD/month profit, 21 month ROI at 10c kWh if diff remains the same (it wont) )
https://www.litecoinpool.org/calc?hashrate=250&speedunit=MH%2Fs&difficulty=102398.53515485&price=3.8996¤cy=USD&power=400&energycost=0.103. 2 Bitmain L3 - 3.88 btc + shipping + customs duty, around 4.1 BTC. ($4100, $238 / month profit at 10c kWh, if diff remains the same)
https://www.litecoinpool.org/calc?hashrate=500&speedunit=MH%2Fs&difficulty=102398.53515485&price=3.8996¤cy=USD&power=800&energycost=0.10Note options 2 and 3 have a warranty, splits it across two rigs (if a KNC titan has a ground fault, all cubes die, if controller dies, your stuffed and many want insane prices for controllers they can't sell)
Due to the risk in purchasing it (diff will probably double by the end of this year, meaning ROI would be 3+ years on this rig, i would have my offer stand at 1 - 1.5 BTC. I am not lowballing but being realistic about my investments.
If you wish to get more, try listing it on ebay, although most buying on there without free electric won't roi, prices are insane plus you have the eBay fees (10% of your sale price).
I hope this helps, im not being an ass but just doing hard math, i like to consider any offer I make as fair, and thus this is my justification for my offer
It is up to you to accept or decline as you see fit as it is your miner. I recommend if you want more though any would wish to not take my offer, then plug it in and mine if your power is cheap enough you will get more if you are willing to wait.
Sorry if the above sounds a bit crappy, i do hope that you didn't pay through the nose for it and havn't yet ROIed because my condolences if you have...