TL;DR: Don't trust the published weight ratings, and be prepared to spend quite a bit more than $80.

What is a good ball head for heavy equipment?

The price range should be less than $80 or so.

I'm sorry to tell you that those are mutually incompatible requirements. You just won't find heavy duty (or even medium-ish duty) ballheads that don't drift, can support 70-200mm f/2.8 lenses at odd angles, for much under ~$150, unless it's the most unrecognizable brand name from Alibaba.com.

Quoting liberally from Photo.SE and other sites:

• From my own answer to the question, Is this a tripod head over capacity or just how they work?

  For instance, the Sirui C-10X says it has a capacity of 28.7 lbs. But what is that, in photographic equipment terms? A Nikon D810 weighs 1.98 lb (990 g). With a 600 mm ƒ/4G ED coming in at 11.16 lb (5.1 kg), the total camera + lens combination weighs 13.14 lb (6 kg), which is just half the rated capacity of the Sirui C-10X. I would not put a 600 ƒ/4 + D810 anywhere near that ballhead. Sure, it will probably clamp and hold the lens when everything is balanced. But if the system were tilted to provide an unbalanced torque on the ballhead, would you be confident the ball wouldn't slip? Not me.

  BTW, that Sirui C-10X is under $80 on Amazon. It meets your price requirement, but obviously I think the "weight rating" is bunk, and I wouldn't trust my 70-200mm on it.

• In 2014, dpreview posted Battle of the titans: Top ball heads tested. It's an excellent review of 10 heavy-duty ballheads. The lowest price head, Sirui K-40x, was $200 at the time of review, now $165 on Amazon. Dpreview rated it their best value, while the $475 FLM Centerball 58 FTR was rated the most stable.

• In 2015, dpreview posted What goes around: 6 mid-sized ball heads put to the test. Surprisingly, the lowest price mid-sized ballhead they reviewed was $260, the Vanguard BBH-300 (as low as $220 at Amazon currently). Their best buy for practical and versatile was the Acratech GP at $400.

• At the lensrentals.com blog in 2009, the always excellent, educational, and entertaining Roger Cicala wrote in Choosing a Ballhead:

  Determining What You Need

  The most important factor in deciding what you will need is load-bearing capability. [...] If you’ll be using lenses weighing more than two pounds (a 70-200 f/2.8 lens or larger, for example) you’ll need a sturdier, higher quality head, but still can find a ballhead capable of meeting your needs for under $200. If you ever plan on using a large lens (300 f/2.8 or larger) you’ll want a heavy-duty high-quality head, and the choice of quick release systems will be critical.

  In his list of medium duty ballheads, only the Induro DM-01 was under $200, at $176 (and now no longer available).

  Importantly, with respect to weight ratings, Roger said:

  Finally, the load bearing capabilities are manufacturer’s statements, not independently verified. Having used many of these I can say that some of the lesser brands are overly generous in their predictions. I’ve used several of these and I can promise none of them (except the RRS and Kirk) can handle the loads they claim they can. About 1/2 to 2/3 of the claim seems right to me for all of the others, but that still puts them all easily capable of handling a medium load.