An item's market value is determined using the following formula:
mV = tiV + W * 0.0036 (Version/0.18.1722)
Where mV is Market Value; tiV is Total ingredient Market Value; and W is Work to make in ticks.
After that, the Market Value can be further modified by quality.
Items with a market value of above 200 will have their market value rounded to the nearest 5, with 2.5s being rounded down. Incendiary launcher for example:
75 * 1.9 + 4 * 21 + 22000 * 0.0036 = 305.7 = 305