Some rare Salvation Army FDCs from the UK sell for very high prices on Ebay. Due to their scarcity, also national collectors are very keen to have them. Sometimes it’s about a rare cachet (e.g., the Portsmouth Philatelic Society cachet – SA 5.9 – cat. price £100, BFDC 2014). Ideally, pristine cachets should have a typewritten address, but the Porthmouths cachet mostly comes with a handwritten address. They should also have a set of the two SA stamps attached. My item is not FDC (second day), but is an illustration of the cachet.
Other times it’s because some PM’s have higher catalogue prices. As Nottingham was William Booth’s birthplace, cachet with this PM has catalogue value £85 (BFDC 2014). The same is true for the Porthsmouth Phil Society PM on other cachets than the Porthmouth cachet above; the catalogue price is then £125 (with set of stamps attached).
Other high priced cachets are those with both the phosphor and non-phosphor set attached. Typically they sell for £ 50 – 100 on Ebay, or even more. In the SA catalogue, non-phospor cachets are numbered as a, phosphor cachets as b and those with both sets as c.