I've said this before, but I don't believe an ebay auction is the best way to sell specialist classic replicas/tributes.
These are rare and desirable cars - there are only around 120 Sammio Spyders out there (and even less Tributes?) and even my humble example turns more heads than a £150k Ferrari -
I'd say you're absolutely right that by putting a 'buy it now' price of five and a half grand on it the seller is telling the world that's what it's worth.
The only people who'll be bidding will have around that to spend on an indulgence car while potential buyers with four or five times that budget won't even have noticed it.
And if anyone doubts that those buyers exist, just bear in mind that there are now kit car companies selling turn-key Ferrari, Jaguar and Aston Martin lookalikes for £80-£120k, while even humble Beetle based 356 Speedsters are now 'from' £28k. (I also had a serious offer of a straight swap for a nearly new car worth over £20k on the very first day I drove mine in 2013).
The car going on ebay looks superb, it has a very nice interior and is extremely well presented. If it was advertised with better wording, better pictures and in a more appropriate place with a set price somewhere north of £20k I have no doubt it would find a buyer (I'd also advertise it on ebay at that price as a classified ad to stand the best chance of European buyers finding it).
I hope to be proven wrong, but as it is, my best guess is that it won't make anything like what it's worth and will probably struggle to make seven thousand pounds. That's a real shame.