The rb816 daughterboard ($69) was just released, it will work with either a rb600 ($195) or rb800 ($359) routerboard. The rb600 is now listed as End Of Life, but a lot of Mikrotik distributors still have it in stock, some have it for sale lower than $195.
$264 for 19 ports, $13.89 per port, 3 gigabit ports & 16 100Mbit switch ports. The rb1100 will be $399, $30.69 per gigabit port. At the last MUM they also announced a rb250GS 5 port gigabit switch for $39.95 running their new SwitchOS instead of RouterOS, perhaps they will make a 16 port version in the future.
I know, but that value is close whith a RB600 (discontinued) and it is necessary to add a casing which are not cheap here ... I think MikroTik daughterboard have not had a major commercial outlet, but they are valid option for some cases.
I think that for simplicity would have to be a integrated hardware with 16 or 24 ports, cpu and ram like that RB450G, to achieve an affordable price.