I collect these also as part of a little Home Front display that I am doing.
Agree with others on the following points:
* Most of the Barclay/Manoil/Grey Iron pieces you encounter are common as dirt (but there are few "better" ones)
* Condition is key, especially for the commons. Really nicely ones (95%+) usually sell (on line) in the 10-20 range (sometimes more)
Additional thoughts would be:
* Don't dismiss all of them out of hand if you run across any. There are "better" ones which can sell in the 50-150 range (or more) ** the foreign (Chinese, Japanese, Italian) ones for example or the ones with folding stock rifles.
Here is a super rare one (below) I just bought this weekend for $300 (O'Brian's M-113, not to be confused with M-114)
* Don't mistake "Tommy Toy" soldiers for the others. These are much better and worth much more. Should all be marked "Tommy Toy" I believe they existed only from 1932 to 1936, had financial problems and sold the business to Barclay.