I am not sure I understand the first part of your question but I can explain the point of the Seller Subsidy.
In my experience, the existence of the seller subsidy has been around for a long time. In my area, the average price of a home is almost 400K and a single family is upwards of 500-600 average. For first time home buyers to have a down payment of minimum 3.5 % = 14,000 + the average closing costs in our area of 3% = 12,000 for a total of 26,000 can be difficult. Remember, they are not drawing on the equity of a previous home.
A seller concession has been a good option for many buyers because it helps them purchase a home, and still keep some of their cash in the bank for reserves and peace of mind.
In kind, with home prices below what many purchased at in the last 6-7 years, a seller concession is a great option for move up buyers as well. Many may need to pay off their mortgage, which can be higher than the price they are selling their existing house for, and in addition bring a down payment. Again, this could be 30,000+ thousand dollars just to "buy themselves out" of their existing home in addition to a 20,000 down payment for their next home. The seller concession has made it possible for many to sell their homes without assistance from a 3rd party (their mortgage lender.)
Yes the seller subsidy can inflate the purchase price of the home to compensate for the money being "donated" to the purchasers settlement funds, however the home still has to appraise for the sales price. An appraiser looks at the comparable sales in a neighborhood or city to assess the value of a home and if the sales price is over the market value then there can be an issue.
It is important as a seller that you are open to the idea of a seller subsidy when putting your home on the market, I would say about 85% of the sales I did in 2011 (22 total) had some type of Seller Subsidy.
My only suggestion as a seller, (and a buyer), is that you make sure your agent is comfortable with the purchase price you and the buyer agree on to make sure you have your best chances possible when it comes to the appraisal.