Not too rare, I've seen them at gun shows. Most were priced around $300. From various gun forums, I hear they are usually not as reliable as the .22 PP, PPK/S. I've got a .22 PPK/S that is 100% reliable and although it's slightly larger, I know it's always going to work.
I don't know what it is with the TPH's from Interarms... but recently they bring a bit more then $300.....I think more like $500
And just a FWIW.... there was a likne new TPH in .25 that just went for over $2k on gunbroker without box and target and that was a Interarms too
Very interesting, I saw several at a Tucson gun show in Feb. 2007 and one was $250 and two were just over $300. They all looked about the same. The $250 was a private seller walking around and the others were on tables. I didn't examine them closely, just looked at them because they were Walthers.