> I think the original link already includes the conversion w/ inflation. It says that the book retailed for fivepence in 1735 which is ₤10 8s. 4d in today's mo

> I think the original link already includes the conversion w/ inflation. It says that the book retailed for fivepence in 1735 which is ₤10 8s. 4d in today's money. No, it didn't say that, that was the total. It said that 500 copies of the book at fivepence was worth ₤10 8s. 4d, and the maths checks out on that: 5500=2500 pence (written 2500d as old pence). There are 20 shillings in a pound, and 12 pence in shilling, so 2400d = £10, with 100d remaining. 8 shillings is 96d, so from 100d leaves 4d remaining, which matches exactly what was originally written. The post-decimalisation equivalent preserved 20 shillings to a pound, so 1s=5p. An interesting fact is the new 5p coins were the same size, and existing shillings continued to be legal tender for another two decades, until the size of the 5p coin was changed. So, the parent to your post was totally wrong with the $10.84, it should be £10 + 40p + 1½p (closest to 5p4/12), so £10.41½ after decimalisation. The closest conversion rate I could find to the time the US introduced the dollar was £1 = $4.55, because it was done at the prevailing values of gold and silver at the time. Using your link, and adding precision to the numbers, £10415 in 1735 would be £1,889,613 today, so £108s4d then would be £1889.61 today as the total gift. Dividing by the 500 copies gives £3.78 each today, which is close to your approximation (most of the difference will be the accuracy lost in rounding 5/240 to 0.02). The inflation rates are also certain to have been difference in the US though, if for no other reason that the current exchange rate is approx. £1 = $1.28, so at the very least it's close to a factor of 4 out in the period since the US dollar was introduced.