I think they should go with Price in game 4. Especially since Thole isn't available to catch Dickey and Martin usually looks bad catching Dickey.
It is a tough decision though, since Dickey has pitched well over his last 7 outings, with the opposition only scoring 14 runs in the 47-1/3 innings (2.66 ERA) that he pitched - http://www.fangraphs.com/statsd.aspx?playerid=1245&position=P
In comparison, the opposition scored 13 earned runs in the final 7 regular season outings that David Price pitched in (44 innings) for a 2.66 ERA also - http://www.fangraphs.com/statsd.aspx?playerid=3184&position=P. In the playoff game # 1, David Price gave up 5 earned runs in 7 innings - http://mlb.mlb.com/mlb/gameday/index.jsp?gid=2015_10_08_texmlb_tormlb_1#game=2015_10_08_texmlb_tormlb_1,game_state=Wrapup,game_tab=box (but 1 hit and 2 runs in the 3rd inning were a result of a Martin-called pick-off play that drew Goins out of position, no one is to blame but it resulted in 2 runs)
ERA, as we all know, is a team stat not just a pitcher stat, however when comparing pitchers on the same team with the same defense it seems legitimate to compare ERA.