JPEG image files grow much bigger after convert to webp about webp HOT 3 CLOSED

I had noticed something like that too. See 
http://trac.macports.org/ticket/27518#comment:13

cwebp is now ok

cwebp test.jpg -o test.webp -q 20
Saving file 'test.webp'
  74700 bytes Y-U-V-All-PSNR 37.01 43.12 42.45   38.23 dB
block count:  intra4: 2582
              intra16: 5610  (-> 68.48%)
              skipped block: 4604 (56.20%)
bytes used:  header:            180  (0.2%)
             mode-partition:  16250  (21.8%)
 Residuals bytes  |segment 1|segment 2|segment 3|segment 4|  total
  intra4-coeffs:  |     268 |   32042 |   14382 |    2014 |   48706  (65.2%)
 intra16-coeffs:  |      28 |    2116 |    2552 |    1019 |    5715  (7.7%)
  chroma coeffs:  |       4 |    2319 |    1288 |     210 |    3821  (5.1%)
    macroblocks:  |      43%|      33%|      17%|       5%|    8192
      quantizer:  |      72 |      58 |      45 |      39 |
   filter level:  |      11 |       6 |       4 |       3 |
------------------+---------+---------+---------+---------+-----------------
 segments total:  |     300 |   36477 |   18222 |    3243 |   58242  (78.0%)