With vintage watches, there is always a compromise for a given budget; here the trade-off was condition, specifically the condition of the dial, for rarity.
A very small number of all original Polarouters change hands each year; I would estimate 5-10. An immaculate example of this same watch sold at WoK in July for around £6000 including commission. That is four times the price of the eBay watch.
You can see much later Polerouters offered by dealers for considerably more than the eBay Polarouter and these watches are commonplace in comparison (and not always as honest and original as this one).
I hope that the dial looks better in person than in the unflattering eBay photos but even if it does not, the buyer has a rare watch and as a very worst case scenario, an excellent Polarouter parts watch with crown, case, case back and marker ring that are all unique to Polarouters.