In Matthew 16:26 (21st Century King James Version), Jesus asks,
For what is a man profited, if he shall gain the whole world, and lose his own soul?
Sir Thomas More's quip in A Man for All Seasons contrasts the grand folly of losing one's soul for the world with the petty absurdity of making the same loss for a small and relatively insignificant piece of the world. Richard Rich, he points out, has sold himself short by committing perjury and betraying his friend for such a trivial prize as the Attorney Generalship of a principality.
Beyond this, there are two further points of significance. Wales has been the butt of English jokes since time immemorial. In the Middle Ages, the English treated the Welsh as a foreign subject population who were barred from holding office in church or state. There were frequent uprisings, culminating in Owen Glendower's rebellion at the beginning of the fifteenth century. Anti-Welsh prejudice would therefore have been familiar to Sir Thomas More, with many further instances over the succeeding centuries being known to Robert Bolt.
Secondly, the Tudors were of Welsh descent. Henry VIII was only the second Tudor monarch, and the Tudors were still seen as upstarts by some of the older English families, particularly those closely connected with the Plantagenets. Snobbish dismissals of Wales as a barbarous place, therefore, could be taken as an indirect attack on the king and his family.