That is to be expected. The SDRs can achieve signal strengths of -150db or so. The pingBuddy is more like -120db range. Compare these to many other well-known ADS-B receivers that are in the mid -90db range. (Note: the higher the negative number the better the signal range.)
Keep in mind that the average pilot cannot make use or see traffic physically beyond about 5 miles away. At even low altitude, both the Ping and the Startux will show traffic well beyond 40-50 miles away. Stratux is extremely sensitive in terms of signal, but very inefficient in term or power needs.
With that said, the Stratux needs about 2.4 amps to really perform optimally, where as the pingBuggy needs far less than 1 amp. Both are great solutions and will provide more traffic and weather than you can see visually from the cockpit. The key is size, form factor and power consumption. You can't go wrong with either device.