CREATE TABLE table_204_568 (id DECIMAL, "pennant" TEXT, "name" TEXT, "hull builder" TEXT, "ordered" TEXT, "laid down" TEXT, "launched" TEXT, "accepted into service" TEXT, "commissioned" TEXT, "est. building cost" TEXT, "fate" TEXT)

how many boats costed less than # 20m to build ?
SELECT COUNT(*) FROM table_204_568 WHERE "est. building cost" < 20
SELECT COUNT(*) FROM "table_204_568" WHERE "est. building cost" < 20