Where it is confusing is costs quoted, in one place we see unit cost, another cost for x aircraft + whatever and it is a lot higher as it covers training and a lifetime of maintainance. From what I have seen, these cost can add 200% to the cost, so a fleet of 10 F-16s' with a unit cost of $45 million would probably cost about $1.5 billion or so. Some prices I have seen run from the J-10 at about $20 million or so depending on equipment chosen, to the Grippen at about $35 mil, the F-16 at $45 mil, to the S-27 at a similar level. However if you look up some recent F-16 sales, you will see different countries pay widely varying prices, some get their F-16s for as low as $27 mil each.
Maintainance cost too are important, if your western engine needs overhauling every 2000 hours, compared to 300 hours for a similar russian engine, thats a big expence over the aircrafts life, probably requiring a hanger of spare engines. So really comparing apples with oranges to just quote unit costs to find the cheapest fighter. I'd probably go with the Gripen, roughly in the middle for up front costs, but over the years costing a lot less to keep in the air. At the end of 25 years, total costs may even be less than the J-10 over that same time period, if the J-10 needs several engine changes in that time.