This has pretty much always been standard, and barring some sort of change in regulation, very likely always will be. As a bettor, your recourse is likely cutting down your bets/farming smaller bets out to your employees, finding a bookie with some gamble/opinion to them, or finding bets with less edge but more volume.
The basic idea with bookmaking without risk is that you want your books balanced - since you get a percentage of the total amount wagered, if your bets on both sides are approximately equal, you can't lose. The risk the "sharps" represent is that they may come in with a large bet on a small market which won't have enough volume to take the other side. Historically it's always been possible to get an edge on these small markets - the canonical example I've always heard is lower division college basketball in the US. The problem is that these lines are so thinly bet than even low 4-figure bets are out of the ordinary, and you need to make an awful lot of them at a single digit percentage advantage to make any real money. Maybe you can come in one day to bet $1000 on Middlebury to beat Lebanon Valley, but good luck coming the next day with a sudden interest in laying down similar amounts of money on Whitman vs. Claremont/Mudd/Scripps. Basically, in general the beatable lines are in areas that nobody really cares about. If you want to come in every week and bet $10k on every NFL point spread, you'll have no problem getting action.
> "I had bet $8,400 to win $4,000 on a tennis match and $2,000 on a [first-five-innings] total on baseball..."
I'm not sure about the baseball bet, but depending on the level of the tennis match, this seems almost guaranteed to raise red flags. Tennis has a somewhat sordid history of suspected fixed matches in lower level competition, and short of major events like Grand Slam late round matches, I'd guess that this kind of action is wildly anomalous.
The basic idea with bookmaking without risk is that you want your books balanced - since you get a percentage of the total amount wagered, if your bets on both sides are approximately equal, you can't lose. The risk the "sharps" represent is that they may come in with a large bet on a small market which won't have enough volume to take the other side. Historically it's always been possible to get an edge on these small markets - the canonical example I've always heard is lower division college basketball in the US. The problem is that these lines are so thinly bet than even low 4-figure bets are out of the ordinary, and you need to make an awful lot of them at a single digit percentage advantage to make any real money. Maybe you can come in one day to bet $1000 on Middlebury to beat Lebanon Valley, but good luck coming the next day with a sudden interest in laying down similar amounts of money on Whitman vs. Claremont/Mudd/Scripps. Basically, in general the beatable lines are in areas that nobody really cares about. If you want to come in every week and bet $10k on every NFL point spread, you'll have no problem getting action.
> "I had bet $8,400 to win $4,000 on a tennis match and $2,000 on a [first-five-innings] total on baseball..."
I'm not sure about the baseball bet, but depending on the level of the tennis match, this seems almost guaranteed to raise red flags. Tennis has a somewhat sordid history of suspected fixed matches in lower level competition, and short of major events like Grand Slam late round matches, I'd guess that this kind of action is wildly anomalous.