Both THS and Premacon comes as RTR and are highly detailed models, which naturally ads a great deal to the price. Uses the same hydraulic systems, high end. Be prepared for about 1 year delivery time, even if their web shops mentions a possiblity as quick as 6 months, which must be considered to be on the more optimistic side of the scale. (THS is e.g at the moment working on 12 off EC480's for the Swedish and US Volvo dealerships, and they are a staff of 6-8 people)
Be aware of that the companies will like to offer you some pretty advanced radios at up to several 1000 dollars, like the Commander series from Scaleart (many attachments are offered for their machines) It's the Germans, very into getting as many small details and functions tru too scale. Things that maybe many modellers other places in the world even not think of or see) Someone locally did get a Premacon with a Commander radio at like 4000 USD just for the radio alone. Way 'overkill' IMO, even though the machine came with some different kind of attachments like a 360 degree grab. Basically on can run the basic excavator functions with a 100 USD 8-10 channel ebay radio. Naturally, when putting 7-10K USD in to a RC excavator, one can find a bit higher end radio that offer more possibilities for a more true to scale operation of the model than a 100 usd ebay version. It's allowed to use some common sence
but hey, if money is no issue, it does not matter too much if one never use 190 of the 200 setups and functions of a high end radio
If going for a kit, take a look at the Fumotec excavators. A bit less details and a bit less complicated way of construction, still same hydraulics as the other high end German machines, but at a more affordable price as it is a kit naturally. An advantage with some experience from building RC models, but if one have good experience concerning mechanics in general, it's no big task to put one together. Concerning the radio system, one can always ask on forums etc.