With crypto-currency the token is the product, so they can justify a transfer fee, yet they still keep it as cheap as possible because they want to get as many people into the system as possible.
Where a crypto-company will make it's money is on the products, services & purchases. (Even PayPal doesn't charge for basic transfers)
If BitShares doesn't yet have any useful products and services then the potential is limited. The solution for the referral programme is to fast track a product (if you can't artificially stimulate BitAsset liquidity) But charging high transfer fees won't aid adoption or the referral programme imo.
REFERRER: Hey dude do you wanna join BitShares?
DUDE: Is BitShares a crypto-currency like Bitcoin that the whole world may end up using like a digital gold?
REFERRER: No. BitShares is a crypto-company!
DUDE. OK? What's the point?
REFERRER: Well we're able to use profits and shareholder directed dilution to fund development of awesome decentralised products and services!
DUDE: Cool you mean like Gambling and Silk Road, all on a blockchain!?
REFERRER: Well unfortunately, BitShares decentralization is just a thin veil so we can't actually offer those..
If you are suggesting that the big idea is to skirt regulations by hiding behind the thin veil of decentralization, that will come to a quick end.
I would recommend NXT or Augur on Etherum for that. What we do offer though is a decentralised exchange and BitAssets, so you can hold currencies like BitUSD on the blockchain!
DUDE: Cool, I'll take a 1000 BitUSD!
REFERRER: Whoa, steady on there buddy, our markets aren't actually liquid or very active yet.
DUDE: Ok so what can I do on this BitShares?
REFERRER: Well if you join today and go through the whole process of buying BitShares we'll let you send these currently useless tokens back and forth for $0.2
DUDE: Wow! Golly, golly gosh! Only $0.2 to send useless tokens back and forth! I can't wait to tell my friends about BitShares!