HK94s run from $3000-3500, depending on condition and configuration. A3 versions with retractible stocks usually sell for about $250 more than A2 fixed stock versions.
If you look really hard, you can find a excellent condition A3 for $3000, but expect at least $3200.
An HK94 is a semi only version of the MP5 with a 16" bbl. This can be later converted to a MP5 with a transferable sear (another $4000). You can also do the paper work for the SBR, and pay about $500-1000 (depending on quality and extra fixens) to get it rebarreled and you will have an MP5 length bbl, on a semi gun.
Another option is a SP89 (semi MP5K) for about $3000. Again you can SBR and add a stock and K-grip, or you can AOW and add the K-grip but no stock.
I strongly advise against any clones, they are of questionable workmanship.