Are you able to back up this statement?
Technically this is impossible. Sell at buy price is okay, but buy at buy price? who absorb the spread cost?
NOt sure I can answer your question correctly. My experience, I sell fund A today, UT converted to $$, with $$ buy into whatever you switch into base on bid price since there is no sales charges. The bid and sell price, if you check them I think it is the so call sales charges. In early 2000 or so, I had quite a number of switches (no free switches allowed), I did manula calculation and updated it online in Fundsupermart even before the system updated my account. Fundsupermart has this watchlist where you can enter your UT and keep track of it. I had consolidated my POEMS and FSM UT together here. The values which I had calculated were very closed to the actual.
You see, the difference came about because of the switching in and out. For intra fund, switching within the same FD group happen within the same day. However, for inter-fund switching, lots will depend on how long it takes them to sell and buy for you. To be precise, how long they take to switch out and in.. typically, can be a few days or up to a week. So you are at the mercy of the system doing the switching, good and bad.
That's my experience. So what I nornmally do is sell that UT and use another sum to buy whatever I wanted to switched into since those days, all were charged. Does not make any different (except for intra fund switch which cost 0.5%). However, currently seems like most are giving some form of free switch, so you don't have to pay at all for charges.