I don't mean to be condescending, but you need to make a choice.
Do you want a reliable, robust, properly-designed and built system, or do you want a cheap-as-chips, unreliable, probably knocked-off-and-cheapened thing?
I have lived 100% offgrid now for almost 20 years.
I run two companies, a house with my family, two workshops, somewhere in the order of 230 computers that run 24/7, and all the things I'd consider "essential" for our existence. Water pumps so we have water. Effluent treatment. Light for nights, power and phones and all those things.
I didn't, and wouldn't, trust all my SENSITIVE, EXPENSIVE equipment on some unknown, random, "built to the lowest possible price, and to hell with the consequences" inverter.
My first inverter (which lasted 16 years, 24/7) was expensive, but back then a *REAL* 5kW 100% dutycycle inverter actually cost money.
My replacement which is a little higher capacity and a LOT more in terms of features, cost in the order of $7K AUD.
If you NEED it, if you RELY on it, if the "opportunity cost" of not having power is significant, or the cost of however many expensive bits of equipment being blown up by something the inverter does, then the answer is simple... DON'T buy purely on price. The cheapest inverters cost WAAAAY too much. At least, in my opinion they do.
I've got instruments that cost upwards of $30K to replace, buggered if I'm going to "plug it in and hope" that my $200 inverter will be ok!