YSP is a one time payment from the bank to the broker for the "retail rate" the customer receives. If you want to get a lower rate, what you are calling a "wholesale rate", you may have to pay a small amount of discount points. The par rate usually pays the broker a small amount of YSP and the next lower rate then usually requires a small amount of dscount points to be paid.
FHA loans are rather unique in that lenders tend to provide incentives (in the form of pricing) to reach certain rates. Look at the following rate sheet example (anything over 100 is the % of YSP paid, anything under 100 is the amount of discount that has to be paid):
6.5% 100.357 6.375% 99.911 6.25% 99.724 6.125% 99.435 6% 102.602
5.875% 102.087 5.75% 101.725 5.625% 100.995 5.5% 101.104 5.375% 100.250
5.25% 99.757 5.125% 98.892 5% 99.028
So the par rate would be 5.375% but I doubt you normally would get that rate. Why? If we gave you that rate, we would make .25% YSP, but if you get a rate just .125% higher (5.5%), we would make 1.104% YSP. Your payment would be slightly higher, but we would make almost 4x as much. Does that mean you are not getting a good offer? Nope. On that day a local bank was offering 5.75% with the same closing costs as my offer of 5.5%. So it ends up as a win-win situation.
Also, notice that if we were to give you 5.625%, we would make less than if we gave you 5.5%. See how that lender gave us a great incentive to offer 5.5%?
This is a rare glimpse on what we see on a daily basis.