This suggests the Philadelphia ore price was fairly stable, 1813-16. For much smaller amounts, Dr. Robert Hare paid a higher retail rate in April, 1816.
In error, Capitan (1979) imgaines the price of platina at Philadelphia in 1820 was $USD 5./oz avoirdupois; no price data for that late date supports that mistaken inference, although domestic metal prices had fallen dramatically, 1817-9.
On Bollman's advise, Wollaston requested platina from Vaughan in Late December, 1817: the order was received and paid 7 months later. This small order may have exhausted the available stock of wholesale platina in the USA, circa April 1818. Despite further requests, no more platina was forthcoming. His Notebooks log a purchase of 684 ounces on 21/25 July 1818 @ USD$ 6./Lb.avd, and further attempts to secure platina from Philadelphia at $5.-6./lb. until at least 1820.
Although he maintained a keen business interest in the metal until his death, it is most likely Bollman was reporting earlier prices from Philadelphia 1815/6. In 1821, Bollman was sent by Barings Bros. to Colombia, to investigate platina sources; he perished of a malady in Kingston Jamaica on his return voyage.
c.1819: 1 Troy Oz. Platinum (US producer price) = USD$ 5.49Americans generally had poor understanding of the Platinum market, as late as 1824.
c.1817: 1 Troy Oz. Platinum (Europe: Intrinsic) ~ USD$ 2.50 (Fr. 13.43)
The Tariff of 1822 included a 15% tax on imported Platina/Platinum:
Citation: The present state of Colombia, by an officer late in the Colombian service p.309
US commodity prices, generally.
Citation: Does protection protect?: An examination of the effect of different forms of ... By William Mason Grosvenor (1871) p.176