I look at it like this:
Precise temperature control is a key element of advanced brewing. To have precise control, you have to have precise measurement. To have precise measurement, you have to have a precision instrument.
Is it possible to get an inexpensive instrument that is also reliably precise? Sure it is possible, and maybe one of the inexpensive options here fit the bill.
However, in my experience, precision costs (not just in brewing, but in everything mechanical - cars, guns, tools, etc). Quality is rarely cheap.
The Thermapen is without a doubt precise, reliable, and durable (and incredibly fast, nearly instantaneous, to boot).
You may find those qualities elsewhere cheaper, you may not, but you WILL find them with the thermapen.
But your own experience and wallet will guide you.