As a rule of thumb which is the same for DR, the more you pay the better it is. You can get an excellent tourney grade marker, notice I said marker not gun, and everything you need (air tank loader) for about $600. You'll also need guppies (the thingys your store the balls in while on the field or something else all you), a mask and you're ready to rock. The mask will run about another $100 for a good one and believe me, they're your eyes so invest wisely.
You can get a top of the line no holds barred marker ranging anywhere from $900 - $1800. You have a few limited editions like any other sport that run in the super high end of the spectrum whereas you also have markers just as good for way less.
A few good names for starter markers, way under the $300 mark, Spyder ( I personally never liked the design but they are extremely user friendly), and Tippmanns (the model 98 can almost be dropped off a 2 story building and still work).
The ones what are better IMHO but a little pricier or a little less user friendly are Autocockers (my personal favorite out of any marker) and impulses. The autococker got a really bad rep over the years, first model was out in 90, of being non-user freindly but believe me, the new models are extremely user friendly compared to the previous years and since most RC'ers are tinker freaks the cocker would suit us just fine. The Impulse is an electropneumatic marker tourney level right out of the box. The cocker and the Impulse will run you about $500 for the base levels of them and into the $1000+ mark for the super high end versions.
My last cocker, which was one of the rare ones I did not build, ran over $1400 for just the marker. No regulator. No air tank. No barrel. No loader. NADA. IMHO it was one of the best, if not the best, markers I have ever used in 16 years that I played. If I was going to get back into the sport I would probably buy, or build, another cocker.
Like I said earlier, it all depends on how much you want to spend.